There are definitely things you can do, but you should just look hard for black food coloring.
Combinations like red, green and blue might come close but will probably turn out a disgusting purplish-brown.
Your best option depends on what you're trying to color.
The only way you can make it gray with food coloring is if the substances you are making the volcano out of is white. You will have to add black food coloring drop by drop until you have the color gray you want. If you can't find black food coloring, mix every color you have together then drip it in. All of the colors mixed together will make black.
black and white blue and white
It will be the same for just about all colorings, put about a teaspoon of vinegar in a cup ( two wont hurt ) add coloring to your desired shade and then hot ( not boiling ) water, enough to cover an egg.
no
Black and White
Producers make,food &oxygen
Sienna and umber are two common pigments used to make brown colorings. They are often heated or burned in order to darken them. Therefore, "burnt" umber or "burnt" sienna are also brownish pigments.
it will burn there food
white and black
No they do not
Black and white.
white and black