Synthetic color or FD&C colors are mostly derived from coal tar. Many have been banned from food by the FDA for various reasons: carcinogenicity, allergy inducing, general toxicity, etc. A number caused illnesses in children. They have been shown in clinical studies to cause various types of cancer.
A few of these colors have now been banned from cosmetic use. For instance, the FDA has already banned the new use of Red No.3, a carcinogen that may interfere with nerve transmission in the brain and cause genetic damage.
Long term studies have shown that regular lipstick wearers ingest approximately 2 ½ pounds of lipstick over 20 years. Any synthetic colors are ingested along with the lipstick.
Synthetic colors, if listed on a product, will appear as FD&C or D&C followed by a number, ie. FD&C Red No. 6. Given the various health risks associated with many synthetic colors, if a personal care product uses it, don't use it.