AWhich types of food coloring would you prefer? Powder, gel or liquid?

In whatever case, you MUST use materials that are "edible" as opposed to "non-toxic".  There MUST be a certification on the label in Canada, US, EU, UK, Australia, NZ, and probably elsewhere.

There are different kinds of powder that are safe for food.  Be careful to make sure you get the right kind for what you want to do.

Some powders are extremely concentrated--basically the stuff that is diluted into gel or paste colours.  These are used for basic colouring of cake batter and icing.

Other powders are intended ONLY to be brushed onto the surface of modelled gumpaste or fondant.  They contain a lot less colour base and a lot more diluting ingredients.  DO NOT use these in batter or to colour a batch of icing.

I like gel and paste professional colours,  I can buy Americolor and Wilton brands locally.  Both are good and not all colours are the same.  But these are professional strength certified bakery colours for batters, icings and painting on foods.

Agreed!  Powder for chocolates and I use gel for most coloring needs!  Liquid works best in batters.