For some reason the front guard cannot be coloured the same as rear, as you can see here it's stuck as base green.

not sure if intentional but also affects the lx6

It is intentional, you can also see in the website section of the cars that the front guards have their fixed texture.

it's a real eyesore for me, always using dark coloured skins (black) it stands out a lot.

It's supposed to be a carbon fibre guard, so it can't be coloured.

Ahh nice, thanks for that

Would be nice to set it to base colour as default though

LX fenders use carbon.dds. The black square in LX_interior1 only modifies some trims and a few bits on the car.
Altho I'd say most if not all cars look better having that square painted black.