How concerned should I be about the presence of FD&C Green #3 and Blue #1 in the outer shells of the vyvanse I take every day? I've read that these are known carcinogens, and some of the worst out of the FD&C colors.

The internet is full of exaggerations and falsehoods.

It is most certainly not the worst of the FD&C dyes. Many have been created, tested, and banned for any human use because they provably cause cancers and liver damage in a matter of months.

As for these two being "known carcinogens", that is a gross exaggeration. Products which contain more than 5% of coal tar are considered carcinogens. Concentrations between 0.5% and 5% are considered safe for human use. But try and explain that distinction to a random blogger who's goal is to promote an anti-something agenda...

Take your medications without fear.