I am trying to find all RGB numbers, that have 2x3 consecutive numbers. By that, I mean this sort of numbers:
\#00FF11
\#66AA44
\#FF0000
I have tried writing this:
\b#(([0-9a-zA-Z])\1){3}\b
but that doesn't work.
Where is the problem? I would probably say, that the problem is somewhere around the \1, because it's the only part I am not so sure about.
The \1 pattern is a backreference to the Capturing group 1, i.e. (([0-9a-zA-Z])\1). You actually want to refer to Capturing group 2 and thus need \2 instead of \1.
Note that \b# will only match # that is preceded with a word char (letter, digit or _). You need to use a non-word boundary at the start, \B.
To match hex chars, [A-Fa-f] is preferable rather than [A-Za-z].
Use
@"\B#(?:([0-9a-fA-F])\1){3}\b"
Using the verbatim string literal, you do not need to double escape backslashes here.