The oil on the new surface of the wood is oxidising which gives it the finished colour and it will change with some cocobolo with time. Nicaraguan cocobolo in particular can be turned white but within a few minutes will start to go orange. If you want to accelerate the process generate a bit of heat by holding the blank and spinning at low speed. I am sure someone from the Health and Safety Police will question this but it gives you an idea of how warm it can get and as you dont want it to get to hot its a heat control. Put it on the window sill before you finish it and watch it change colour. Putting a finish on will slow the change as most are UV inhibitors. With time it will return to the colour of the blank.