2D can you make an outline around only a certain color on a sprite?

Let's say I have a sprite that has different blobs of color in it. Could I somehow get the color at a certain point and then make an outline around that certain color blob? Each blob would have a unique color that is only inside that one blob, so the outline would only be around one part. I imagine it probably isn't very easy, if even possible, but it would help me out so much!