Re: Is food coloring to put in Oatmeal a known carcinogen?

No substance proven to be a carcinogen in man or animal can be used in 
food products (Delaney Clause amendment to Food Additives Act).

No food coloring is a "proven" carcinogen.

Over the years, most of the older food colors have been replaced with 
those accepted to be safer. The only food color with controversy about it 
that's still in use is Red #3.

"Certified Food Colors" must be produced under FDA regulations 
and "certified" to that effect with a letter of guarantee. 

These food colorings are widely used in a number of foods, chiefly those 
associated with voluntary consumption (Jello, beverages, candies, bakery 
items, snacks, etc.) rather than normal meal items.

I sympathize with your desire to minimize inclusion of extraneous 
additives with no other purpose than color.

Although I don't believe these colorants are unsafe in modest quantitites 
even over an extended period of time, you might be happier in 
using "natural" colorants as a substitute if young children are involved. 

Carotene will make an orange color, and can be extracted from carrots. 
Beet juice (from canned beets) will make a nice red color. Blueberries 
make blue dyes. Etc. If you then add a dye, it's got a nutritious purpose 
as well.

Be careful in trying to make your own colorants when feeding infants and 
children under 2 years old. Uncanned vegetables may cause "infant 
botulism" or other unknown agricultural contaminants may cause other 
problems.

Certified food colors have received a lot of attention for safety and so 
are the "devils we know". Substituting uninvestigated additives may end up 
with the "devils we don't know".