I have the slate gray/chalk interior on a GT silver Targa 4S and I like the look. Suspect it would also work with chalk exterior (chalk has a lot of gray in it, especially notable in sunlight). I went with the slate gray deviated seat centers to break it up a bit with the lighter exterior. May want to consider that. I also have the 14 way seats and they work well for me.

 

I finalized my build a month ago and went with chalk exterior and full bordeaux red interior (PMYG1VD3 if you want to see in configurator) There aren’t really any light interior colors that look good with a chalk exterior imho but the bordeaux is in between light/dark so could be an option for your friend. If you want to go two tone with the interior the black/bordeaux is a really good look as it was my original choice before I decided to go big or go home with the full bordeaux. I agree with first commenter that Iceland green/black two tone would not mesh well with chalk. Color is such a subjective thing as something that one person loves could be absolutely hideous to another. Good luck designing the build!

 

Deviated seat centers was a brilliant pick Dgtarga , it looks nicer to break up chalk