Purge tower incorrect filament?

[MarkWood1]

Hello everyone,

I am printing with a twin extruder single nozzle A10M and using Cura as slicing software. The item I am trying to print is white with a small amount of black at the top.

When printing the nozzle moves to start the tower and purges out black (only the black extruder is turning), it then starts to print the product in white which causes it to turn from black through grew scales to white. Once it has produced the first layer it returns to the purge tower and repeats this process. It looks good as a Zebraomegle xender print, but how do I make it so that it will only purge out white until it gets to the bits I want black?

P.S. If I print two of the same product the second is produced with the correct colours in the correct order meaning the first is effectively a purge.

Can any one offer any assistance or had this problem before? I am not new to printing but I am new to twin extruder printing.

Thank you in advance for any and all help.