@AmyMPreschool Counting and calculating with colors is not native to Excel and requires VBA programming. I would recommend you to enter the number 1 in each '10-minute' cell when worked and apply Conditional formatting to give the color you want.
Then you can sum the rows for each person, giving a total of let's say 24. That would be 24 x 10 min = 240 min. Divide by 60 and you'll end-up with 4 hours.