I have a grey scale image, with transparency. How can I convert this to one solid specific color, and preserve its edges/transparency?
As an example of what I’m trying to achieve:
If I understand your question correctly:
First, make sure that you are in RGB mode. (image > mode)
Right-click the layer you want to convert to a solid color, and click blending options.
In this window, go to the color overlay tab on the left, and in the right pane choose a color.
Looks like this. (image from here)
Is that what you were looking for?