Tiger Barbs Colors Change Each Day

[NewTankGuy]

I have 7 tiger barbs in my tank, 3 striped, and 4 green.  For all 7 of them, I noticed their colors change throughout the day.  Each morning all of their colors are very vibrant, and rich, but throughout the day, most of them have their colors fade dramatically to a very washed out version, but come the next day they look amazing again.  Does anyone know what causes this, or if its some type of issue with them?

 

[GriffinC18]

I have no idea what it is, but it would be awesome to have that and it not be health concerning lol!

 

[catfish4ever]

mine do that all the time, at night they fade in colour, the day thye look dazzling!