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:

but others are not colorized at all

and, in a weird case, a value (0x77) colorize two bytes (0x77 and 0x57)

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

Regards!
Josep