I've been stuck playing a single server for over 2-3 years now, trying to find a fix for this bug. I have what they call rainbow tiles, i'm using win7 but i dont really think it is an hardware problem at all.

My system specs

Intel Celeron E3400 2.66Ghz~
Intel G33/G31
I'd say it's probably your super old Intel onboard video chip. BYOND has been known to not play great with those.
Yeah, Intel graphics for some reason can't handle any of BYOND's shaders, so your computer is screwing up the Goon lighting. I've never been able to get any diagnostic info from Intel users about this; the shader seems to compile, it just isn't being applied for some reason.
In response to NSBR
In response to NSBR
Probably because my chipset lacks hardware t&l... That could be the cause. But is there any way to disable the lighting?

Also CM-SS13 runs fine on my computer without any graphical bugs too and that's what i dont understand