I can understand the use of bright colors in picking out friend from foe in the madness of mass melee, but once gunpowder became king why didn't camoflauge or even heavily muted colors become the norm?
You're overlooking a fair few factors about early gunpowder weaponry that have only been solved fairly recently (ie, when smokeless powder came along). There are other relevant factors - the various qualities of muskets and other early gunpowder weaponry (range, smoke, accuracy) and other factors that mean that the dimensions of combat in the days of musketry aren't quite the same as the ones of today. And sometimes, it's just outright fashion. u/StoryWonker and u/dandan_noodles explain further in this thread. As always, should anyone have more insight to contribute, further posts are always welcome!