[greymule]

I think that if F3 was using the orange part when she wasn't supposed to be (say, to make an extra-long base so she could grab an errant throw), I would rule that BR could touch only the white.

Since it is proper for F3 to use the orange base on a play from the foul side of the line, I would not require BR to figure out, on the way to 1B, whether F3's being on the orange was legal in that situation or not. The fact is, F3 is there, and BR is merely trying to avoid a collision.