Masking 2 moving movie clips

I have 2 movie clips that move randomly around the screen. When the shapes overlap the color of the overlapping area should change - is that possible? Any help would be huge - I’m in over my head trying to get this done for a client

Where ever the dynamic motion is generated, apply it to another clip on stage. If the clip is dynamically attached, then just use the same code to attach a duplicate.

You might be able to do what you want using purely blending modes, but if not, you can achieve this by duplicating both clips and any motion tweens on to separate layers, one above the other, but above the originals. On the lower layer, add a colour effect. The upper layer masks the lower and isn’t visible. Now when they intersect you will have the necessary area visible. If the motion is controlled dynamically, you can use setMask method for as2 / the movieclip mask property for as3

Their movements are dynamically generated so I’m not sure how to attached another movie clip to one to sort of “shadow” it