In terms of colourful fish, you could put a trio of Pseudotropheus salousi.
or a trio of red top ndumbi reef, but you will have a spectacular male and dull females
or you could do pseudotropheus minitus.
But be aware that you would need to construct great rockwork. Doing this in a 36g would be considered an advanced technique and general advice would be to avoid it.
You might be better if with lake Tanganyika shell dwellers.
Electric Blue Rams and well chosen apistos would be a different way to get a colourful tank.