One is permitted to place turmeric in food and there is no need to worry [that doing so] is [transgressing the] coloring [prohibition] as there is no coloring [prohibition involved] in [dyeing] food.
Getting pigment on ones bread: If one dyes his bread with the pigment of fruits, such as strawberries and pomegranates, there is no problem involved being that there is no [prohibition of] coloring by foods.
Summary – Dyeing Foods:
Has no dyeing prohibition. Thus one may color his food.
May one on Shabbos place food coloring into foods or liquids that are planned to be sold?
No. Doing so contains the dyeing prohibition.
May one dye water or other liquids?
- Example: May one mix concentrated juice with water?
It is permitted to dye water on Shabbos for purposes of drinking [as opposed to selling]. However some Poskim rule one is not to do so. Others rule one may add the water to the concentrate but not the concentrate to the water. Practically according to the Shulchan Aruch and Alter Rebbe doing so is completely permitted without restriction when doing so to drink that day.
 Ketzos Hashulchan 146/8.
 Perhaps the reason for this prohibition is due to that food coloring is a normal dyeing ingredient, and is commonly done.
 Shaareiy Tziyon 318/65
 Darkei Moshe 320/2 in name of Yireim; Michaber 320/19; Chacham Tzevi 92; Admur 320/26; M”B 320/56; Aruch Hashulchan 320/7; Kaf Hachaim in understanding of the Shulchan Aruch, however he brings also the dissenting opinions.
 Mohara Mintz brought in Darkei Moshe ibid; Nefesh Adam brought in M”B ibid rules to be stringent when one intends to die the food; Ben Ish Chaiy Pekudei and in Shut Rav Poalim 3/11, brought in Kaf Hachaim ibid.
 Brought in Ben Ish Chaiy and Kaf Hachaim ibid; Mishneh Berurah in Shaareiy Tziyon 318/65
 However for the next day is forbidden according to all as one may not trouble himself on Shabbos for the week.