I have both of these in my 60 Gl.
Though these plants are very healthy and needs to be pruned every 10 days, L. Aromatica remains green and P.Stellatus has a light purple color (under the leaves).
My Alternanthera is deep red and Ludwigia is light red.
I use CFL (2 x65 for 12 hrs, 4 x 65 for 8 hrs, all 6700K) and Seachem fertilizers.
What could be the reason for L. Aromatica and P.Stellatus to remain green instead of deep purple/reddish colors?