I don't agree with the idea that dark coloration for a juvie JD means stressed. Usually the opposite. For a juvie JD it generally means well adapted and dominant. Now a light, pale or washed out color COULD mean stressed for a juvie JD.
Amongst very young JD, the dominant fish ( usually male) will be darkest. Seen it time after time in my own tanks, and especially so at LFS over the years. I've seen the dominant male amongst juvie JD's all dark, chasing the **** out of every other juvie dempsey in the tank ( who are all pale and scared, trying to hide) at pet shops so many times. Don't tell me the dark dominant fish acting tough and all confident is stressed

Now the pale ones trying to hide, all scared and nervous are definately stressed.
Of course once they grow a bit, JD start to get more colorfull ---- bright metalic blues, though the darker coloration can return when they breed, especially for females.