I'd personally get the gold if your making a Mark 6. But if your making something else maybe blue. I'd personally stick with gold, just my opinion though.
I stopped by a motorcycle shop before I bought my visor and found out that even the smallest visor is plenty big for my helmet, and I have a larger helmet thanks to my big head. If you're worried about the visor being too small at all... you shouldn't have to worry about that at all. ^^;
I'll post pictures when my visors finally get here. that way you can have a size comparison as I'll have a ruler in the picture.
The visors that I saw in the motcycle shop... some were a LOT larger than others. I would swear that one was almost 10 inches tall... it was clear though.