The denim/mottled effect is obtained by dyeing an egg in red, dark blue or purple, and then washing/rubbing that dye off.  (See techniques for details.)  Small amounts of the dye will remain around the wax lines, giving and outline effect, and in the pores, giving the mottled effect.  I then dye in light blue (or other blue) just long enough to get a light final coat.

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