What Causes The Red On A Tetra's Belly?

[r.w.girard]

So, I have a school of two dozen Green Neon Tetras, Paracheirodon simulans in a planted community tank.  Green neons are similar to both Neon Tetras,P. inensi, and Cardinal Tetras P. axelrodi, except that they are smaller and the iridophoric [?] stripe continues to the base of the caudal pendicule. And I was wondering what effects the belly's color?  Is it a function of sexual fitness or social hierarchy? Health or general comfort? Or am I just feeding them the wrong things? I assume that the coloration is influenced by the same factors in the two other species, which is why I mention them.

 

[thereverendturtle]

It seems in my experience that overall health and how comfortable they are in their surroundings. Sick or stressed fish will generally look very washed out.