I'm something of an amateur and am slowly self-teaching myself Photoshop through experimenting with different projects. My current project is a fan edit of some game assets that aren't packed or compressed and can easily be replaced to alter the icons that represent some in-game abilities.
The icons in question are laid over some coloured backgrounds, the colour of which represents the level of the ability -- these coloured backgrounds are packed away however, and adding alternative backgrounds requires that they be baked into the icon image since tampering with the packed files is a bannable offence.
A fair few people have released icon packs which include novel backgrounds for the ability icons, with or without changes to the actual icon aside from baking the backgrounds in, but all of them include solid backgrounds that cover up the original backgrounds completely and just have a basic black border rather than a faithfully stylized one.
You may see where I'm going with this now... I've been experimenting with making icons with backgrounds that include transparent parts which reveal the colour of the original background beneath, both in an effort to be more faithful to the original style of the game's interface and to avoid fully covering up the indicated level of the ability.
I've had fun using transparency via masks and such to make backgrounds that fade away in some fashion to reveal the background underneath, but I've something that I want to do but can't figure out how is to make backgrounds that adopt the colour of the background beneath themselves.
I've tried searching around a bunch, but I haven't been able to find info on what I'm trying to achieve -- my terminology might not be specific enough. To give an example of what I'd like to do, 'galaxy packs' are popular, wherein the backgrounds of the icons depict space or otherwise galactic imagery. A fun idea I had would be one such pack wherein the colour of the galactic imagery or some parts of it blend with the background beneath and appear that colour.
So to get down to the point, I'm familiar with manipulating colours and basic transparency effects via masks, blend layers and the like, but I can't really figure out how to make it so that the contents of an image would adopt the colour of an image underneath after having been exported from Photoshop, rather than just appearing as partially transparent grayscale on top of another colourful image. I feel like I'm just shy of having the knowledge to be able to do it, but I can't put my finger on what I'm forgetting or missing.
Thanks for the help!