Change color of current and voltage arrow (circuitikz)

Question

Currently, only the names of currents and voltages are red/blue. I'd also like their arrows to be red/blue. How can this be done?

\documentclass{article}
\usepackage[utf8]{inputenc}

\usepackage{float}

\usepackage{graphicx}
\usepackage{tikz}
\usepackage{circuitikz}

\tikzset{every picture/.style={line width=0.75pt}} %set default line width to 0.75pt 
\usetikzlibrary{quotes, angles, calc, babel}

\ctikzset{bipoles/thickness=0.8}
\ctikzset{bipoles/length=0.8cm}
\ctikzset{bipoles/diode/height=.375}
\ctikzset{bipoles/diode/width=.3}
\ctikzset{tripoles/thyristor/height=.8}
\ctikzset{tripoles/thyristor/width=1}
\ctikzset{bipoles/vsourceam/height/.initial=.7}
\ctikzset{bipoles/vsourceam/width/.initial=.7}
\ctikzset{inductors/scale=0.8, inductor=american}
\tikzstyle{every path}=[line width=0.8pt,line cap=round,line join=round]

\usepackage[backend=biber, sorting=none]{biblatex}


\begin{document}

\begin{circuitikz}[american, straight voltages, scale=0.84]
 \draw (0,0) 
  to[battery, l={\textcolor{blue}{$U_e$}}] (0,4) -- (1.5,4)
  to[C, l=$C_1$, i={\textcolor{red}{$I_{C_1}$}}, -*] (1.5,0) -- (0,0) -- (3.5,0)
  to[switch, l=$S_2$] (3.5,1.5) -- (3.5,2.5) node[circ]{}
  to[switch, l=$S_1$, -*] (3.5,4) -- (1.5,4) node[circ]{} -- (5.5,4)
  to[C, l=$C_3$, v={\textcolor{blue}{$\frac{U_e}{2}$}}] (5.5,2.5) -- (5.5,1.5) node[circ]{}
  to[C, l=$C_4$, v={\textcolor{blue}{$\frac{U_e}{2}$}}] (5.5,0) -- (3.5,0) node[circ]{};
 
 \draw (8.25,4) to[L , v={\textcolor{blue}{$U_s$}}] (8.25,2);
 \draw (8.25,1.5) to[L, v={\textcolor{blue}{$U_s$}}] (8.25,-0.5);
 \draw (3.5,2.5) -- (7,2.5) to[L, v={\textcolor{blue}{$U_p$}}] (7,1.5) -- (5.5,1.5);
 \draw (7.45,3.5) -- (7.45,0.5);
 \draw (7.55,3.5) -- (7.55,0.5);
  
 \draw (8.25,4) -- (11,4)
  to[L, l=$L_1$, v={\textcolor{blue}{$U_{L_1}$}}] (14,4) -- (16.5,4) node[circ]{} -- (18,4) node[ocirc]{} -- (16.5,4)
  to[C, l=$C_2$, i={\textcolor{red}{$I_{C_2}$}}, -*] (16.5,-1.5) -- (18,-1.5) node[ocirc]{} -- (13.5,-1.5) node[circ]{}
  to[switch, l=$S_4$] (13.5,2) -- (8.25,2);
  
 \draw(14,4)
  node[flowarrow]{\textcolor{red}{$I_{L_1}$}};
  
 \draw (13.5,-1) node[circ]{} -- (14.5,-1)
  to[D-] (14.5,1) -- (13.5,1) node[circ]{};
  
 \draw (13.5,-1.5) -- (10.5,-1.5)
  to[switch, l=$S_3$] (10.5,1.5) -- (8.25,1.5);
  
 \draw (10.5,-1) node[circ]{} -- (11.5,-1)
  to[D-] (11.5,1) -- (10.5,1) node[circ]{};
  
 \draw (8.25,-0.5) -- (9,-0.5) -- (9,4) node[circ]{};
 
 \draw [<->, color=blue] (18,3.8) -- (18,-1.3) node[midway, fill=white]{$U_a$};
     
\end{circuitikz}


\end{document}

EDIT:

With the help of https://texdoc.org/serve/circuitikz/0#subsection.5.8 i managed to color the voltages, but not the currents.

\documentclass{article}
\usepackage[utf8]{inputenc}

\usepackage{float}

\usepackage{graphicx}
\usepackage{tikz}
\usepackage{circuitikz}

\tikzset{every picture/.style={line width=0.75pt}} %set default line width to 0.75pt 
\usetikzlibrary{quotes, angles, calc, babel}

\ctikzset{bipoles/thickness=0.8}
\ctikzset{bipoles/length=0.8cm}
\ctikzset{bipoles/diode/height=.375}
\ctikzset{bipoles/diode/width=.3}
\ctikzset{tripoles/thyristor/height=.8}
\ctikzset{tripoles/thyristor/width=1}
\ctikzset{bipoles/vsourceam/height/.initial=.7}
\ctikzset{bipoles/vsourceam/width/.initial=.7}
\ctikzset{inductors/scale=0.8, inductor=american}
\tikzstyle{every path}=[line width=0.8pt,line cap=round,line join=round]

\usepackage[backend=biber, sorting=none]{biblatex}

\NewDocumentCommand{\fixedvlen}{O{0.44cm} m m O{}}{% [semilength]{node}{label}[extra options]
 % get the center of the standard arrow
 \coordinate (#2-Vcenter) at ($(#2-Vfrom)!0.5!(#2-Vto)$);
 % draw an arrow of a fixed size around that center and on the same line
 \draw[-Triangle, #4] ($(#2-Vcenter)!#1!(#2-Vfrom)$) -- ($(#2-Vcenter)!#1!(#2-Vto)$);
 % position the label as in the normal voltages
 \node[anchor=\ctikzgetanchor{#2}{Vlab}, #4] at (#2-Vlab) {#3};
}

\begin{document}
\begin{circuitikz}[american, straight voltages, scale=0.84]
 \draw (0,0) 
  to[battery, l={\textcolor{blue}{$U_e$}}] (0,4) -- (1.5,4)
  to[C, l=$C_1$, i={\textcolor{red}{$I_{C_1}$}}, -*] (1.5,0) -- (0,0) -- (3.5,0)
  to[switch, l=$S_2$] (3.5,1.5) -- (3.5,2.5) node[circ]{}
  to[switch, l=$S_1$, -*] (3.5,4) -- (1.5,4) node[circ]{} -- (5.5,4)
  to[C, l=$C_3$, v=, name=vC3] (5.5,2.5) -- (5.5,1.5) node[circ]{}
  to[C, l=$C_4$, v=, name=vC4] (5.5,0) -- (3.5,0) node[circ]{};
 
 \draw (8.4,4) to[L , v=, name=vS2] (8.4,2);
 \draw (8.4,1.5) to[L, v=, name=vS] (8.4,-0.5);
 \draw (3.5,2.5) -- (7,2.5) to[L, v=, name=vP] (7,1.5) -- (5.5,1.5);
 \draw (7.45,3.5) -- (7.45,0.5);
 \draw (7.55,3.5) -- (7.55,0.5);
  
 \draw (8.4,4) -- (11.15,4)
  to[L, l=$L_1$, v=, name=vL1] (14.15,4) -- (16.65,4) node[circ]{} -- (18.15,4) node[ocirc]{} -- (16.65,4)
  to[C, l=$C_2$, i={\textcolor{red}{$I_{C_2}$}}, -*] (16.65,-1.5) -- (18.15,-1.5) node[ocirc]{} -- (13.65,-1.5) node[circ]{}
  to[switch, l=$S_4$] (13.65,2) -- (8.4,2);
  
 \draw(14.15,4)
  node[flowarrow]{\textcolor{red}{$I_{L_1}$}};
  
 \draw (13.65,-1) node[circ]{} -- (14.65,-1)
  to[D-] (14.65,1) -- (13.65,1) node[circ]{};
  
 \draw (13.65,-1.5) -- (10.65,-1.5)
  to[switch, l=$S_3$] (10.65,1.5) -- (8.4,1.5);
  
 \draw (10.65,-1) node[circ]{} -- (11.65,-1)
  to[D-] (11.65,1) -- (10.65,1) node[circ]{};
  
 \draw (8.4,-0.5) -- (9.15,-0.5) -- (9.15,4) node[circ]{};
 
 \draw [<->, color=blue] (18.15,3.8) -- (18.15,-1.3) node[midway, fill=white]{$U_a$};
 
 \fixedvlen{vL1}{$U_{L_1}$}[blue]
 \fixedvlen{vS}{$U_s$}[blue]
 \fixedvlen{vS2}{$U_s$}[blue]
 \fixedvlen{vP}{$U_p$}[blue]
 \fixedvlen{vC3}{$\frac{U_e}{2}$}[blue]
 \fixedvlen{vC4}{$\frac{U_e}{2}$}[blue]

\end{circuitikz}
\end{document}

Answer 1

You should use the same techniques used for the blue arrows that you got from the manual and adapt them for the currents. You have all the labels specified in the diagrams in section 5.8.1.

A real minimal example follows, showing also how to manually add a current of a voltage with the same style.

\documentclass{article}
\usepackage[T1]{fontenc}

\usepackage{circuitikz}
\tikzset{every picture/.style={line width=0.75pt}} %set default line width to 0.75pt
% so it's 0.75pt or 0.9pt???
\tikzstyle{every path}=[line width=0.8pt,line cap=round,line join=round]

\NewDocumentCommand{\fixedvlen}{O{0.44cm} m m O{}}{% [semilength]{node}{label}[extra options]
 % get the center of the standard arrow
 \coordinate (#2-Vcenter) at ($(#2-Vfrom)!0.5!(#2-Vto)$);
 % draw an arrow of a fixed size around that center and on the same line
 \draw[-Triangle, #4] ($(#2-Vcenter)!#1!(#2-Vfrom)$) -- ($(#2-Vcenter)!#1!(#2-Vto)$);
 % position the label as in the normal voltages
 \node[anchor=\ctikzgetanchor{#2}{Vlab}, #4] at (#2-Vlab) {#3};
}
\NewDocumentCommand{\redcurrent}{mm}{% node, label
    % position the circuitikz arrow shape in the normal position and direction
    % but color it red
    \node[currarrow, color=red, rotate=\ctikzgetdirection{#1}] at (#1-Ipos){};
    % ditto for the label
    \node[red,anchor=\ctikzgetanchor{#1}{Ilab}] at (#1-Ipos) {#2};
}

\begin{document}
\begin{circuitikz}[american, straight voltages, scale=0.84]
    \draw (0,0)
    to[C, l=$C_1$, i=, -*, name=ic1, v=] (3.5,0);

    % this an independent, manually positioned red current arrow
    \draw(0,1) node[currarrow, color=red]{} node[above,red] {$I_{L_1}$};
    \draw[blue, -Triangle] (4,1.5) -- (4,-0.5) node[midway, right]{$U_r$};

    \fixedvlen{ic1}{$U_{L_1}$}[blue]
    \redcurrent{ic1}{$I_{C_1}$}

\end{circuitikz}
\end{document}

Notice that:

1. you have conflicting setups for the line width;
2. \usepackage[utf8]{inputenc} is default since a couple of years, but you probably want \usepackage[T1]{fontenc};
3. You are styling components with both "class" parameters (ok) and internal parameters (dangerous, they can change in the future);
4. scale=0.84 changes only the coordinates, not node sizes nor fonts; you probably meant scale=0.84, transform shape there; that will scale anything but the linewidths (more or less).