tinted gem

hello, i'm creating a mod about magical power, i have in mind to make a custom mana color who is selected by a player when it's enter the game, and modifiable later with a gui.

i want have a text zone to enter the hexadecimal color code and and save it's on a custom variable witch is specific to each player. after that I want the armor, gems, and special weapons to have parts colored with this base color (I created the textures in different layers, like the layer whose color should change and the one whose color should not change)

can you help me ?