For Ember Knights players, I made a guide for how to find all of the player colors! Hopefully this will be helpful for everyone.
Default Colors
The default blue, orange, purple, and green colors are available from the start. Before unlocking the ember pit, however, you cannot choose your color, and you must use the one that corresponds with your spot in the player order.
The ember pit will be unlocked when you first unlock one of the other player colors.
Yellow
In Scoggfirth, you will occasionally find a room containing a waterfall with a strange mark on it. This waterfall can be blown open with a Blast Bomb, revealing a hidden cave. Enter the cave to unlock the color.
Frosted
In the Steadfast Citadel, you will occasionally find a room containing a wall of ice that bears the same stange marking as the waterfall in Scoggfirth. Use the Ember Fire skill to melt the ice, revealing a hidden room. Enter this room to unlock the color.
Pink
In Wightsbury, you will occasionally find a room containing a mausoleum, the doors of which contain an all-too-familiar marking. Use a Warrior Wisp (it doesn’t matter how it’s summoned) to light up the torches next to the mausoleum’s entrance. Doing so will cause the doors to open, allowing you to enter and unlock the color.
Electric
In Anville, you will occasionally come across a room containing two tesla coils and a door that bears the same marking used to indicate the location of other hidden player colors. Use lightning (the Judgement skill is the best way to do this) on the tesla coils to activate them, causing the door to open. You can then enter the hidden room to unlock the color.
Elder
This is one of the easiest ones to unlock. Just attack Esper a few times and he’ll give it to you.
Seasonal
At the end of the Steadfast Citadel, in the room where the care package spawns, there will be a hidden snowman. Attack the snowman to unlock the color.
Nebula
Note: I don’t know what the official name for this color is, so I just made up one that sounded cool. If anyone knows what the actual name is, let me know and I’ll update this.
This color is unlocked upon defeating Praxis in Netherra for the first time.
Midnight & Daybreak
Note: I don’t know what the official names for these colors are, so I just made up some names that sounded cool. If anyone knows what the actual names are, let me know and I’ll update this.
These colors are unlocked upon completing the game on doom difficulty and getting the true ending.
Hellfire
Note: I don’t know what the official name for this color is, so I just made up one that sounded cool. If anyone knows what the actual name is, let me know and I’ll update this.
This color is unlocked upon defeating Praxis in Netherra while playing in endless mode.