Well, good luck with it. 
I’m not sure, but I can offer you two options. The first one isn’t the easiest one, you should bring in your signature image, create a new layer and fill it with the color you want to replace this color with. Set the layer mode to screen. Flatten the image by going to layer, flatten image. Then duplicate the layer by control-clicking on the layer in the layers panel and make the original layer invisible by clicking on the eyeball icon beside it. Use the magic wand to select the white area of your image and delete it. Delete the layer you’ve hidden by dragging it to the trashcan in the layers panel. Yeah, that’s kind of a long process so, if you want to make things a lot more easier then I’d recommend you to try photoshop-plugins software. This standalone version of the editor combines advanced editing features with an understandable interface, making it an ideal program for beginners. I haven’t heard about a lot, but once I tried it, I was surprised why it’s not so widespread.
I’ve got a set of Photoshop tutorials for any need. So far, they’ve helped me with all possible issues. I’m sure you’ll find the right tutorial there: https://www.format.com/magazine/resources/photography/photoshop-tutorials Take a look at lessons 8 and 9 about coloring and text.