The colour scheme ? Or just some FPS induced nausea ?
The latter. The older I get it seems the more susceptible I am to it. Top down is fine (WoW, DS3) and FO:NV was thiiiis close to being ok (if only you could zoom out like 5 more feet) but first person only (Borderlands, TF2) and about an hour in Ill have a pounding headache and a queasy feeling in my stomach.