Not all plants in the Red section are true red plants. I am no expert but for example;
Didiplis diandra
Ludwigia arcuata
Ludwigia repens
Rotala rotundifolia
These usually turn red only when stressed by light overexposure, lack of NO3, toxic traces etc. Is it correct for such plants to be in the same category with the real reds?
Well, first let me say that not everything in that category has to be
literally red, which I think takes care of the
Rotala.
L. arcuata is definitely red, and you don't have to go to extreme measures to make it that way.
L. repens is a red plant even in many low tech tanks. In fact, the native Ludwigias are more often not red when found growing submerged. In fact,
L. palustris is sometimes not only red in very strong light, but also has very narrow leaves like
L. arcuata! I wouldn't say plants like that are necessarily stressed, just responding to conditions. I gather from some of your postings that you're rather conservative in dosing and so on, and that's fine. It's just that the strong light and fertilizing many of us utilize isn't so excessive to most.
The only one I sort of agree with you on is the
Didiplis. Under most conditions, only the tips are red; it's not naturally solid orange. I'll change that.