RegEx issues

Hello,
I'm trying to colorize an hex log, and I find a estrange behaviors.
E.g. I can colorize ok some bytes:
2688f46f-0ccb-4798-88b5-22dacb6dd10a-image.png

but others are not colorized at all
1b2451ef-d820-4ceb-aba3-b5a1e9f09cc9-image.png

and, in a weird case, a value (0x77) colorize two bytes (0x77 and 0x57)
f86c427c-f0c8-44c8-8539-926dc408cc87-image.png

It seems that colorizes better low values (below 0x80) than high ones.

Another thing that could affect (?), could be that the log has been captured using "odd" parity... but ... not sure about it, as it colorizes correctly if I use 0x01 or 0x03
c39a59f2-2ed9-4a98-bd5a-4e525eb8b86d-image.png
3bc2eb3d-1eef-4dea-867a-53dc57a5b52d-image.png

Regards!
Josep