I tried the colour clothing thing. To be honest I didn't notice any difference at all.
My working clothing is usually fairly natural in materials and colours; think more the Autumnal range of greens, rusts, tans, but I deliberately bought pale fawns, creams, beige coloured clothing to try.
I was on a three week dig in the middle of Summer, and it was utterly scorching. We were working beside a flooded henge, with a double ring ditch. The centre never dried out, and was used in Winter time as a curling pond. The pond was a heaving with life, and masses of insects, and it was on a dairy farm.
Every single one of us got bitten that year, really badly bitten. It didn't matter whether I wore the dark clothing or the light, I got bitten just as often and as miserably.
I think the insects prefer to land on dark as part of their sneaking around, but that doesn't mean that they're not there just because we don't notice them. They happily rest on the ground at your feet, on the tree/grass/bush beside you, on your spade and bucket, they'll just sleekity sneak in under the radar and get you anyway.
It was an SSSi, so no insecticides. I have never been so tempted in my life to find the fly spray.