Radium
So... back in the day we accidentally switched the Electrum and Radium pigments when we made our first batches. Consequently writing descriptions for these colors has been hard because the name doesn't match the color anymore, but it's been far too long to change them back, so here we are.
This paint starts out reddish in the bottle, but when applied over black it does a slow transition from yellow to gold to green before your eyes.