Yep to get this chrome effect really well done it will need to be drawn alot of it in photoshop. Using different shades of whites and greys. What makes chrome look like chrome isn't the colours it has, but the way it looks when it darkens. It's hard to explain but that skin shows it well. If you look at a bright part of chrome it's just 255 255 255 rgb. Plain white. But how it blends with the dark parts makes it look like chrome.
If I was going to make the skin. I'd take photos from the car and scale them to the size of the texture parts. And then draw those shades of greys in the same parts as the real car. And then take the time to blend them properly (not with blur) so that it looks like "chrome". If it doesn't look like chrome when it's just a skin in photoshop it won't look 100% like chrome in the game imo and more just a car that is light or dark grey.
That would be alot of work obviously! Good luck if anyone ever tries it.
It would look static on it's own, but with the lighting over the top ingame it would blend more. The opactiy level of the chrome shading could be faded and tweaked if need be.
The other thing is the lighting effect ingame. If you have the same lighting effect for the red parts as you do the chrome parts.. It won't be right. I don't know if this is possible in gp4 to have two different textures, one with carlightmap on and the other without. You'll notice in the other mp421 topic the chrome looks good but the red is too pale because it has the same glossyness as the chrome.
With these two things (texture effect and lighting), I think it would be close as possible to real thing given the game engine. I have done some tests as this challenge is quite fun
But nothing yet to show for progress. Without committing hours and hours to making it look right.
It's also a real challenge to get the lighting looking perfect for both track cameras, and for onboard or cockpit view. If it looks good in tv track cameras it will be too dark in onboard view. We will see once the season starts but my guess is that from onboard tv view on a sunny day the top surfaces of the car will be yellowish silver, reflecting the sun.