I think worm castings look a bit like chopped cigarette tobacco. If your bin is white or if you have ever kept worms in a light color container with a cover for a couple of days the sides of the container above the food level will have 1/4 inch castings on them. You should be able to see individual ones. Even when harvested you should be able to see the individual ones depending upon what harvesting method you use. Coffee grounds would be maybe rounder? It all depends upon how close one wants to look.

I know one thing. However good your vermicompost is this week, if you stop feeding for a week and let the worms work just on what you plan to harvest, you will like it even better in a few more weeks.

When I am in a rush for compost I put some in an old plastic easter basket with good sized holes in it and shake the material. What falls out is my harvest. What stays in is put back on top of the bin. I almost think this partially processed material is very good for the health of the bin. It balances out the excesses in all directions, too wet, to dry, to acidic, of new additions.

Good luck, hope you have some already.