No Secret David.
They are 16 Bit images and to colour them I use Curves- red, green and blue. To add yellow I go to the Channel Mixer and select Blue and pull red slider to the left. Final tweeks in Hue/Saturation. Red first then yellow and the Master last. Each image is different so you will use different amounts on each one. There is probably an easier way but I don't it yet.
Here are the images a bit smaller I forgot the first time.
