What is considered the best coloring agent for icing?

The best coloring agent for icing is paste. Paste food coloring is highly concentrated and allows for a more vibrant and intense color without altering the icing's consistency significantly. This is especially beneficial when coloring buttercream or fondant, as a small amount can achieve the desired hue.

Moreover, paste coloring offers a range of shades and can mix well to create custom colors. It also tends to be more stable when exposed to heat and light compared to other forms of coloring agents, such as liquid dyes, which can often dilute the icing and affect its texture and flavor. The paste's thickness means it doesn’t introduce excess moisture, keeping the icing stable.

In contrast, liquid colorings can change the consistency of the icing, especially if a substantial amount is needed to achieve the desired color. Vegetable oil is not a coloring agent at all but rather a fat, and gel coloring, while effective, often does not have the same level of pigmentation as paste. Thus, paste coloring is preferred among bakers for its efficiency and effectiveness in achieving deep, consistent colors in icing.