Have you thought about posting in the hybrid section? Those guys might have some advice on how to go about this or at what point you want to outcross to another species. GL
The most colorful Paraneetroplus (exVieja, exParatheraps) are IME 'melanurus' (red form and orange form), 'bifasciatus' Rio Chacamax along with 'breidohri' and 'regani'. Here are some pics of mine.
'melanurus' (red form)
'melanurus' (orange form) View attachment 918190
'bifasciatus' Rio Chacamax
'breidohri'
'regani'