This guide shows how to quickly change the overall look of the map with just 2 console commands.
So gm_bigisland is a success of a map, no doubts but there is something of it I never liked (In My opinion – take it with a grain of salt). Their blueish color filter and excessive bloom on very bright textures like sand being an example.
So, with these TWO console commands you can tweak the map to its original look and have a less agressive bloom.
Type in your console:
ent_fire tonemap setbloomscale 0.35
(you can play with the value)
ent_fire color_correction kill