if you got yourself a pot of dark brown brummer and white brummer, you can mix them until you get the right shade to match your timber, and you can just fill it in, wait for it to dry then sand it down.
I cannot recommend a filler for sapele. However dust and PVA can work well if it is only a small gap you need to fill. I strongly advise against using the Metalux/ Everbuild two part filler on this wood as the colour match is no good once it is sanded.
I find that, sometimes, the PVA and sawdust mixture goes horribly wrong and turns black once you put a finish on! :shock: I think this is only when you put too much glue in the mix?