il viola del cavolo rosso

Per colorare il cibo senza ricorrere a coloranti artificiali ci sono vari metodi, per il viola si può utilizzare il liquido viola che si ottiene cuocendo il cavolo rosso a pezzi in poca acqua; per il rosso i fiori di ibisco, per il giallo curcuma (o il classico zafferano), per il verde la polvere di the verde... il riso viola lo devo provare!
(via Homemade food coloring healthing and toxin free)

Make Purple Food Coloring from Red Cabbage

To make purple food coloring, all you need is one half of a big red-cabbage head. First, chop cabbage into big chunks and put them into a pot of boiling water. The amount of water should be just enough to cover the cabbage. After about an hour, the cabbage should lose its color while the water should turn dark purple. Remove from heat and let cool. Once it is completely cool, discard the cabbage (I saved mine to put in soup or stew). To illustrate the effectiveness of this homemade purple colorant, I used it to make purple steamed rice, by simply replacing water with this natural food dye and then letting the rice cooker do the rest of the job. My steamed rice came out gorgeously purple and didn't smell too much like boiled cabbage. I named it "Riso Purpuraceous."