IMHO yes you did a (big) mistake...I certainly hope it is still time to repare it...
Gt silver looks gorgeous! I've seen both white and Gt silver and I would chose silver over white any day...That my 2 cts. And for that matter if the silver has pccb, adaptive, and SC it's even more a no brainer!! Get the silver while it is time!! You'll thank me later!
Not to talk about the resale. Silver with all these options will be much easier to resale, go back to dealer tell him to keep his white TT, and go back grab the silver!