Food paste appears as a cafeteria tray with a blob of pink paste on it. Terminal entries at Suffolk County Charter School suggest that the paste is completely devoid of flavor (though the intervention note stated that the paste "tastes great"), turns skin pink with regular consumption, and has psychological effects such as irritability.
The area that this consumable is found in has a unique population of pink feral ghouls, which supports the observation of the paste turning the skin pink.
One can find a dead raider with a letter on them regarding the paste as a random encounter. This note mentions that another raider (who carries five food pastes) has become addicted to the food paste and that his friends are having an intervention. This suggests that food paste has some addictive qualities.
No matter how much paste is consumed by the Sole Survivor, they will never experience any of the side effects of food paste consumption.
If one shoots or attacks the paste with any weapon, they can see that it bleeds.
A feral ghoul that has become pink from ingesting the food paste
The food paste dispensers and pink stained handprints.
↑Fallout 4 Vault Dweller's Survival Guide Collector's Edition p.384: "[6.19] Suffolk County Charter School The student base of this school consisted mostly of lower-income and disadvantaged students. These children were lucky enough to be chosen for trials of a new food substitute paste developed by Vault-Tec in conjunction with the U.S. government. The paste was intended to provide all necessary nutrition and have a shelf life of over 100 years. Despite some minor side effects, the paste is both nutritious and delicious. Why not try some yourself? You’ll be in the pink!" (Fallout 4 Vault Dweller's Survival Guide Map)