I have two veils that I use from time to time. One is a yellow veil that is attached to a pull-over jacket, and the other is a black veil that I drape over my head and shoulders.
When I am using the yellow veil I find it harder to see larvae and eggs in the comb, but when I wear the black they show up better, and I can see them clearly.
Any reason for this? Does the yellow mess with your depth perception, or something along those lines?