How to avoid unwanted Spaces in \NewDocumentEnvironment?

I tried to make my own "quote"-Environment and I wanted the first Letter to be bold and a little bit bigger than the rest. As \lettrine doesn't work the way i wanted, i tried to code it on my own.

Everything works as intended, except one thing: I get a white space between the L and the orem Ipsum and i don't know where it comes from

\documentclass[12pt,a4paper,listof=totoc,oneside]{scrreprt}
\usepackage[ngerman]{babel}

\usepackage{xcolor}
\definecolor{citecolor}{HTML}{6495ED}

% Weil ich parameter im end-teil haben will
\usepackage{xparse}

% Eigene Quotes
\usepackage{csquotes}
\NewDocumentEnvironment{myquote}{m o}{%
\begin{samepage}%
\list{}{%
\setlength{\leftmargin}{1.5em}%
\setlength{\rightmargin}{1.5em}%
\setlength{\topsep}{0em}%
\setlength{\parsep}{0pt}%
\setlength{\partopsep}{0pt}%
\setlength{\parskip}{0pt}%
}%
\item\relax%
\begin{itshape}%
% Anführungszeichen
\begin{large}\textbf{\textcolor{citecolor}{\flqq}}\end{large}
% Großer Buchstabe (wenn angegeben)
\IfNoValueTF{#2}{}{{\Large{\textbf#2}}}%
}{%
\begin{large}\textbf{\textcolor{citecolor}{\frqq}}\end{large}
\end{itshape}%
\endlist%
% Quelle
\hspace*{\fill}\mbox{\footnotesize\textcolor{citecolor}{\cite{#1}}}%
\vspace{1.5em}%
\end{samepage}%
}%

\begin{document}

% Calling the Environment
\begin{myquote}{WIKI1}[L]
orem Ipsum...
\end{myquote}

\end{document}

-
You are missing the % required to end lines: as you've not used \ExplSyntaxOn the 'standard' requires of TeX programming apply. –  Joseph Wright Mar 18 '13 at 7:58
Welcome to TeX.sx! –  texenthusiast Mar 18 '13 at 7:59
Ty for the quick Response, but even if I end each line with a %, the blank between the L and the orem Ipsum stays. –  Arno Nym Mar 18 '13 at 8:06
While code snippets are useful in explanations, it is always best to compose a fully compilable MWE that illustrates the problem including the \documentclass and the appropriate packages so that those trying to help don't have to recreate it. –  Peter Grill Mar 18 '13 at 8:28
ty for the hint, i posted a executeable version –  Arno Nym Mar 18 '13 at 8:36

The space is the end of line after \begin{myquote}{WIKI1}[L], because your "begin part" starts a paragraph and this space is not ignored. The solution is to add \ignorespaces.

I've made some other changes to your definition; avoid \begin{itshape} or \begin{large}: \itshape and \large are declarations that don't take an argument.

\documentclass[12pt,a4paper,listof=totoc,oneside]{scrreprt}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}

\usepackage{xcolor}
\definecolor{citecolor}{HTML}{6495ED}

% Weil ich parameter im end-teil haben will
\usepackage{xparse}

% Eigene Quotes
\usepackage{csquotes}
\NewDocumentEnvironment{myquote}{m o}
{%
\par
\begin{samepage}%
\list{}{%
\setlength{\leftmargin}{1.5em}%
\setlength{\rightmargin}{1.5em}%
\setlength{\topsep}{0em}%
\setlength{\parsep}{0pt}%
\setlength{\partopsep}{0pt}%
\setlength{\parskip}{0pt}%
}%
\item\relax
\itshape
% Anführungszeichen
{\large\bfseries\textcolor{citecolor}{\flqq}}%
% Großer Buchstabe (wenn angegeben)
\IfNoValueTF{#2}{}{{\Large\bfseries#2}}%
\ignorespaces
}
{%
{\large\bfseries\textcolor{citecolor}{\frqq}}%
\endlist
% Quelle
\hspace*{\fill}\mbox{\footnotesize\textcolor{citecolor}{\cite{#1}}}%
\vspace{1.5em}%
\end{samepage}%
}

\begin{document}

% Calling the Environment
\begin{myquote}{WIKI1}[L]
orem Ipsum...
\end{myquote}

\end{document}


-
thank you for the additional input! I will apply your improvements to my code! :-) –  Arno Nym Mar 18 '13 at 11:35
The space after the L is from the newline after [L] in your document. You can ignore white space there by adding \ignorespaces to your definition. There are also some missing % which cause extra space after your grey <<
            \begin{large}\textbf{\textcolor{citecolor}{\flqq}}\end{large}%<<