Is it permissible to color food on Shabbat
Is it permissible to add red wine to white wine or tea concentrate to water on Shabbat or is it considered coloring on Shabbat?
As a general rule poskim agree that the concept of coloring does not apply to food. However, there is a disagreement in regards to liquid. Some poskim such as the Nishmat Adam held that the permissibility of coloring food does not apply to liquid since in regards to food a person doesn’t normally mean to color the food rather the main intent is to spice it. For example one who adds chrein into the gefilte fish and colors it red doesn’t mean to color it but to spice it unlike by liquid when many times a person wants it colored. In addition, Shavet Halevi explains that since the process of manufactoring paint always involves liquid, liquids are treated more strictly.
Lemaase the Ben Ish Chay maintains that אין צביעה באוכלים applies only to solid item such as diping bread into wine and not to liquid items such as the above cases. Others such as Chacham Ovadyah apply the rule to both and permit coloring liquid food items as well.