My thoughts are:
If you're sure you will always want a white hull, then use a white pigment on the epoxy, and if that doesn't make it white enough for you, then paint the hull also. If you get scratches in the hull they won't show as much because you have white-pigmented epoxy.
If you think that somewhere down the road you might want to show a wood hull, then use clear epoxy and paint white. Then you can always sand off the paint and varnish for a clear finish to show off the wood.

: I'm intending finishing off my kayak with a white hull - would it be better
: to use pigment during the epoxy progress, or paint it after it is
: finished?

: Would there be a significant weight difference if I added several coats of
: paint?

: thanks for any tips