It's happened to me too. I dont have a premium subscription and I thought it was just because I was playing on a friend's server who has lighting effects. However when I DM'ed my own campaign in a regular account, it happened. First, it starts when I select tokens, they start showing the same blue vectors, and the handle to rotate the token in another color. Then, it usually becomes worse when we add token's label names, up to a point where the whole screen is just colors. Sometimes clicking on the map helps removing the error, but shows up again when clicking a token. It's become almost impossible to use roll20 due to this. I'm on an Intel Core i5 9 Gen with an Nvidia GEFORCE GTX card.