What does a mucus plug look like?

So I had just used the bathroom and a small snot textured type discharge came out. Maybe a little bigger than an ant but it was tinged a greenish color and it was followed by some veryyyyyyyyyy light brown discharge. I would of taken a picture but I had left my phone all the way upstairs. I'm 29 +1 today with an ultrasound for tomorrow. Was that part of my mucus plug? Should I worry? Baby girl is still moving and I have no cramps or pains except for a sore back I had from yesterday which I was at my baby shower.