Optimizing a schedule of guided tours

Hello Excel experts!

I'm trying to use Excel to help me create an optimized schedule of guided tours through an historic site. I have a list of the times spent in each room/building for three different types of tours. I need to figure out what times to start the tours so that I can have as many as possible per day without them running into each other. There can be multiple tours happening at once, but they can't be in the same rooms at the same time. 

The current method that I'm using is a list of the spaces in the columns and the times in 5 minute increments for the rows while inputting each tour in different colors. Then I'm experimenting with what time to start the tours in order to find the best combination that gives me the most tours per day.

I've included a snippet of a screenshot in order to help explain the method I'm using, but I feel like there's got to be an easier/better way to do this. It's taking way too long and I'm worried that I'm missing some of the more ideal combinations. Any ideas or help would be greatly appreciated!