Colour problems with my multicade icade 60in1 jamma pcb

[Dazwilky]

I have just installed an Icade 60in1 PCB, which I bought second hand from eBay, into my jamma cab. Basically, the colours are screwed up on the games, more noticeably on Donkey kong because Mario and the girders are purple and not red and frogger as most things look purple, logs, lily pads, everything. On the opening test colour bar screen, most of the squares are purple and colours look dull and flat. Not nice and colourful and vibrant like I've seen on other icade 60in1's. Does anyone know what I'm doing wrong? I am a complete novice and never done anything like this before. Any help or suggestions would be gratefully received.