Changing colour of text. Beginners problem

There are probably a number of ways of doing what I am trying to achieve, but none have produced good results for this newbie.

Scanned a page from a book and cut out the number I want to highlight as a layer. Importing into After Effect, I just need to change the dark area (the number) of one layer to a colour that emphasizes. (I'm going to scale as well but the colour is the problem)

Getting below result using "Change to Color" but there's a lot of spill and not all relevant gets selected. Have tried many different black/grey "From Color" values, but very fiddly and results are not great. 

Any help much appreciated.