If it were me, I would definitely go for Black, Basalt Black or Atlas Grey.

The styling of the 997TT is certainly not clean and simple IMO. It's very ornate (+ve view) or too fussy (-ve view). I think the best way to mask some of this 'so-called over-styling' is to pick a very, very dark colour so that it hides the intakes, holes, scoops, panel gaps etc.

More generally, from a 'car image' perspective, I think a very dark 997TT looks really 'menacing'. IMO some of this effect is simply lost when a lighter colour is chosen.

For my 997S, there was only one colour in the end: GT Silver.

If I were to chose a 997TT (theoretically), it would probably be Basalt Black

Just my 2 cents....

(BTW, I said "theoretically", because I wouldn't trade up from a 997S to a 997TT. If/when I trade up, it would be to a Lamborghini Gallardo/Murcielago or whichever Ferrari is on sale at that time).