Flux:

Prompt example:

GT40 MKII in motion, GT40_MKII Vehicle, black with white rally stripes, driven by 1man.

It responds well to the colors (in italics above) being changed.

SDXL Version:

I'm very proud of this SDXL model, it's everything I set out initially to make for myself with the 1.5, but never got working as I had hoped.

The training images were of a red GT-40 Mark II with white rally stripes, but it responds well to prompting different colors. I've even experimented with asking it for graffiti and ghost flames, see the example photos. I even posted a error 6 wheeler, check that out, lol

It will sometimes try to give 3 stripes instead of 2, and I find that specifying "white rally stripes" tends to correct that.