AMy red royal icing dried with these darker grayish blotches in it. I used Wilton No taste red..... I didn't add black or any other colors to it. What could it be?

this would be my best guess. The mix may not have been the same thickness throughout. my suggestion is to put it back in your mixer get the colour you want. Then because red colour tends to thin the icing slightly bring it back to full thickness and leave it to stand for 24 hours before you use it because the colour can develop over time. it may also help to use RED EXTRA.

try not to use a damp finger to flatten your peaks in the icing, rather wrap your finger in cling film as even the smallest amount of moisture will change the colour.