You don't need to remove the numbers. Even if you did, a simple fixed, pre-made mask would let you erase them. What you need to do is to get the (x,y) coordinates of the computer line and the hand drawn line. Do you have those? If not, do you have the two line images as separate images? Otherwise one of the lines will have "breaks" in it where they overlap.
You can find each color with the Color Thresholder on the Apps tab of the tool ribbon.
You'll have to go along the spiral because you can't simply find out which the distance of the purple pixel to the closest blue pixel because sometimes the purple pixel is closer to the curve either closer or farther away from the center than the blue curve that it's supposed to be on.
