I have a couple regex hilighters:
Hilight an AHK label,
LABEL:
[A-Za-z_0-9]+:$Hilight variables, like FOO+=, FOO:=, FOO.=
[A-Za-z0-9_#[]@-]+(| |t)+(+|-|.|:)=[ ]?
Now hilight the .=, :=, etc so it’s not the same colour as the variable
(+|-|.|:)=Hilight variables inside percent signs.
\%[a-zA-z0-9#_@$?[[]+\%
While you can’t specifically call your regex a line-comment as such, you can just choose a text color for your regex that matches what you want for the line-comment.
And do:
^.
Hilight right side, as Yutaka indicated.