I think the confusion is due to the Tool Tray being called a Toolbox. The game calls it a Tool Tray (when mine is full and I try to buy another item).

I have a rainbow girl. The first one married Boone in the 25th generation and I've kept it going generation after generation. We're now in the 29th generation.

Pairing the last 3 heads on the head chart seem to produce more rainbow-haired girls/spikey-haired boys. The 4th head from the bottom combined with the last head on the bottom will sometimes produce rainbow-haired girls/spikey-haired boys.

Here's a pic of the Family Tree for Generations 25-29: