Nerds aren’t always vegan, but they can be! You can buy specific flavors online such as on Amazon. The only flavor that I could find on Amazon which does not contain Carmine is the Grape mini-boxes. The Strawberry nerds are the ones that contain the Carmine, while the grape nerds only contain two coloring agents (blue and red 1/2), and thus the grape ones are vegan while the strawberry ones aren’t.
While I have never seen them sold individually Amped Apple & Road Rash Raspberry should also be vegan as they do not have any red/pink pigments. They’re generally sold bundled with another flavor that contains carmine though, which isn’t vegan.