For years, I've been working on a worldbuilding/alternate history project but am currently struggling because I need a global map to get the job really done. Sure, on Photoshop, I can use Paint Brush to create mountains, but a big, squiggly line won't give an accurate portrayal of a mountain range's shape or size, which is why, using municipal base maps, I have found that using Paint Bucket is more desirable than Paint Brush.
A more reliable tool that I've often used is Magic Wand, and that's where we first get to the question. Presented here is an image of one of South America's nations under a geological map:
In this scenario, I have decided to use Magic Wand to select any of the colors presented in the legend and then Command-J that color, turning it transparent. To save time, I have thought about using Magic Wand to select all of that one same color at once and Commanding-J from there. Is this sort of thing possible? If the first answer is yes, then what steps would I take to go there?