If you are going to make the sawdust yourself, pick a softer wood than maple. I would go with a light pine. It can be darkened with the okoume that you have. It is better to go slightly darker with the filler than lighter as your eye isn't drawn to it as much. Another possibility is to use the darker stuff you have and add flour or durham's water putty (dry) to it, to lighten the color an acceptable amount. Make a small test batch first. Hope this makes sense.
Bruce