easy enough you get the round plastic balls and cut them in half then you get the sticker decal that has that pattern and put it on the out side and then spray it red and then peel off the stickers like the master chief visor i will send you a link to how he did the visor. then die the plastic ball red.
you go to around 3:10 and watch from there to see how he put the same design on his visor. it should help you out, cutting the ball in half is not hard a hack saw will do it but be careful not tocut your self even better if you have a dremel with a cutting wheel go that route...