Is one permitted to add food coloring to food on Shabbos?

One of the 39 prohibited labors on Shabbos is Tzovea or Coloring because in the process of the building of the Mishkan we find that they would dye the wool which was used for making the coverings of the Mishkan.

With regards to food however, the halacha is that 'ein tzevia b'ochlin' the actual translation of which states that coloring does not take place in edibles, which in turn means that one may blend foods and liquids even though one food item will color another.

It is therefore permitted to add ginger to food, pour raspberry syrup into water, mix red and white wine and pour tea essence [1] into hot water. [2]

Am I permitted to add food coloring solely for the sake of coloring the food?

The halacha is that even adding coloring for the sake of coloring is permitted but the Mishna Berura writes that it is better not to do so. [3] This does not mean that one may dye foods at whim. One is prohibited to dye food or liquids for marketing purposes. For example, one who sells liquor may not dye the liquor in order to make it more appealing to customers. Even though one is dying a food product and we could say that 'ein tzevia b'ochlin', it is not so, because that is only true when the sole purpose is to whet an appetite. When the purpose is other than eating it takes on the regular laws of dyeing and coloring. [4]

The Mishna Berura adds from the P’ri Megadim that one who dyes water and places it in the sun will in all likelihood have to bring a korban as atonement.

s there an issue of Coloring when wiping stained hands on a napkin on Shabbos?

This halacha might seem a bit foreign to us because we are not accustomed to dyeing clothes and fabrics. Nevertheless, since it is normal to dye fabric and cloth, coloring a napkin with one’s red hands must be avoided. [5] It appears from the Shulchan Aruch that this halacha applies to substances that are regularly used for dyeing, such as fruit extracts. However, soiling a napkin with gravy would not be a problem because one does not usually dye fabric or clothing with gravy.

Therefore, after eating raspberries, strawberries and any other colored fruit one should rinse one’s hands and lips with water before wiping them on a towel or napkin.

Is there a difference between a paper napkin and a material one?

Yes there is because a paper napkin is discarded subsequent to its use and therefore its coloring is not called dyeing. One only dies items that are intended for later use whereas paper napkins are soiled not dyed. [6]

What if I only have cloth napkins and I cannot rinse my hands or lips?

The Mishna Berura writes [7] that others disagree and say that wiping soiled hands on a napkin is not called tzovea rather it is something known as derech l'chluch – soiling - and is not subject to the restrictions of tzovea. Therefore when one is in a situation where there is no other option one may rely on this opinion and wipe one’s hands and face even on a cloth napkin.