gecko's face changing colors?

[Monk21]

I noticed that sometimes the leopard gecko's head/face area will change colors. Usually it is yellow with some very light accents of red. Also his nostrils are reddish and the bottom jaw is white with black spots. Now, sometimes these red accents get deeper and so are the black spots. Is this something to worry about? As soon as I can get clear pictures I will post them

PS, I have NO light in his tank. I just use a black heat lamp.
PS2, the temperature in his tank is at around 80F on the "warm" side but this changes depending on the outside weather

 

[Ophiophilist]

Although not as vivid as cresties, leos can change a bit according to their mood and condition. My girls get more yellow after baths and handling.