How can I make \newcommand work together with \ticknum

Question

I'm trying to make a lot of different variations of PGFplots label styles so I'm trying to define different values and use \ticknum to pick one of them for example

\newcommand{\x0}{0.3}
\newcommand{\x1}{0.5}
\newcommand{\x2}{0.7}

...

every x tick label/.style={
    rotate=45,anchor=north east, text opacity=\x\ticknum,
},

But this gives me this error every time

! Undefined control sequence.\tikz@textopacity ->\x\ticknum \end{axis}

If this succeeds I also want to define different variables to change rotate value for every x tick differently for example. How can I make this to work?

EDIT : This is what works like a charm with colors but I'm trying to make something like this to work with numeric values as well.

\definecolor{col0}{RGB}{0,0,255}
\definecolor{col1}{RGB}{255,0,0}
\definecolor{col2}{RGB}{0,255,0}

...

every extra x tick/.style={
    grid=none, 
    tick label style={draw=col\ticknum},
},

This is a complete code

\documentclass{article}
\usepackage[a4paper,tmargin=5cm,bmargin=0cm,lmargin=0cm,rmargin=0.2cm,footskip=0cm]{geometry}
\usepackage{graphicx}
\usepackage{pgfplots}
\usepackage{adjustbox}
\pgfplotsset{compat=1.8}
\usepgfplotslibrary{groupplots}

\begin{document}



\begin{adjustbox}{center}
\begin{tikzpicture}
\definecolor{COL0}{RGB}{255,0,0}
\definecolor{COL1}{RGB}{0,255,0}
\newcommand{\x0}{1}
\newcommand{\x1}{1}
\begin{axis}[
    /pgfplots/ymin=0,
    height=10cm,width=20cm,
    ybar stacked,
    /pgf/bar width=0.952381cm,           
    legend style={at={(0.5,0.98)},
      anchor=north,legend columns=-1,font=\Large},
    symbolic x coords={1,2},
    xtick=data,
    x=1.14286cm,                           
    enlarge x limits={abs=0.666667cm},  
    every x tick label/.style={
        rotate=45,anchor=north east, text opacity=1, inner sep=5pt    %\x\ticknum (trying make this to work)
    },
    xticklabels={Text A,},
    every extra x tick/.style={
        grid=none, 
        tick label style={draw=COL\ticknum},    %Here this works 
    },
    extra x ticks={2},
    extra x tick labels={Text Extra},
    ]

\addplot+[fill=COL0,ybar] plot coordinates {(1,0.00519089)(2,0.0850676)};
\addplot+[fill=COL1,ybar] plot coordinates {(1,1.74808)(2,1.06387)};
\legend{\strut A,\strut B}

\end{axis}
\end{tikzpicture}
\end{adjustbox}
\end{document}

Answer 1

I figured out a workaround so I don't have to specify opacity. I'm just making every label as extra label and then do this and specifying different color for every characteristic

\definecolor{FILL0}{RGB}{255,255,255}
\definecolor{FILL1}{RGB}{255,0,0}

\definecolor{DRAW0}{RGB}{255,255,255}
\definecolor{DRAW1}{RGB}{128,255,50}

\definecolor{TEXT0}{RGB}{255,128,128}
\definecolor{TEXT1}{RGB}{128,255,128}

every extra x tick/.style={    
    grid=none,
    tick label style={fill=FILL\ticknum, draw=DRAW\ticknum,  text=TEXT\ticknum},     
},

This way I can pick colors that look like it has opacity 0.5 for example. So instead of making text black with opacity 0.5 I'm making text greyish with opacity 1. No one sees the difference