AndCamera photo editor can adjust the color of a photo.

Cyan: G+B
Magenta: R+B
Yellow: R+G

white, grey ： R=G=B 

Under sunshine and bulb, photos are too yellow (R+G too high)

• a: lower R+G, this reduce intensity
• b: increase B, Use B to neutralize R+G, increase intensity and decrease yellow.
• Use both a+b, it's possible to lower yellow without changing intensity.

Under shadow, photos are too blue (B too high)