Batik is an interesting process where you need to think what you don’t want covered by coloured dye. Your design should keep that in mind.
Special wax need to be added to the fabric right there where you want to see the fabric. The colouring takes place within the lines of the wax.
Special tools, called tjanting are used to apply the wax. Using some basic colours and mixing them you should be able to create a wide palette of colours for your mask.