Swapping color on textures

[cluadius]

I am trying to customize my pack for 1.15 right now using the tannerite texture from the metallurgy pack for diamond. I got everything swapped in but i would like the Diamond horse armor color palette to match. i tried to modify it in photoshop and it wont allow me to make any changes. Does anyone know why this is happening?

[HanFox]

You'll need to change the image mode of the PNG.

Image menu > Mode > RGB

[JuanZelada]

In photoshop at the beginning you have to specify in which color mode you are going to work, some have default CMYK (for print), you have to change it to RGB (for web)