Here you will find a simple palette modification for "B-17 Flying Fortress" by MPS, changing the colors of the sky and landscape as well as the airplane colors. There seemed to be a weird syndrome going around in the 90s between British game developers, forcing them to make all their flight sims in extremely dull and drab colors, with very purple colored skies. Either that or all their monitors were broken. Hopefully the game now looks a bit more like the blue skies and green farmland of 1940s continental Europe. Gone is the purple hue sky and the overly brown-green tint on both landscape and planes. This mod won't work with most normal B-17 installs, due to the game files being compressed or whatnot. But there exists one release that was not compressed, and thus is conveniently open for modding. I have included a link to it below. You should only use it if you own the game legally.

B-17 Visual Realism Mod 1.0
B-17 Flying Fortress - PW Review

B-17 Flying Fortress - Game Files (Required)
B-17 Flying Fortress - Original Poster
B-17 Flying Fortress - CGW Advert 1
B-17 Flying Fortress - CGW Advert 2