Purple and green are Marlin's race colours.
I think nearly everyone will agree the colours are not the most desirable for a road car, however look at it this way:
Marlin launched the prototype in this colour and it was a huge success. They took another person on to cope with the orders. Since seeing the silver demo car the interest has been even greater, with even more orders. If they had launched the silver car first, would they have been able to cope with the orders?
As for it being minimalistic. It's a kit. If you want it like a '7' with bare chassis inside etc then that is ok. If you want it with all the luxuries of your family car, just add them.
After all there is a good £4k+ spare if you have bugeted for a GTM Libra.