Merging 2 blobby's, and having their colors mesh together?

[X14Halo]

Just wondering how I can achieve this...

Basically I have 2 blobby looking spheres, each with their own color gradients, and then they will meet and merge into 1 big blobby shape. I need to find a way for their colors to slowly blend together when they meet and become a combination of all the colors from both.

Any ideas?

[dgruwier]

How are you creating the spheres and how are you merging them?