Here is what they say about tinting their shellac.
"Tinting – A wide variety of shades and tones can be
achieved by tinting
SealCoat with alcohol-base stain, aniline
dye, or small amounts of universal colorants - up to 2 oz. (60
ml) colorant per gallon. Note that alcohol stains will dilute
viscosity. If using powdered dyes, shake to completely
disperse dye material and let container sit for a few minutes
for bubbles to clear."
Might be worth a try eh?
Bill