Hi Munira, welcome to the forums!
Great question. The calendar itself is actually an archive template, which is a fancy way of saying that it’s a page you won’t find in WordPress itself, much like a Category page for default WordPress posts.
Instead, customizing the layout means customizing the template itself and, for that, we have a very comprehensive article called the Themer’s Guide that provides the ins and outs for modifying any template in the plugin.
We understand that touching code is not everyone’s strong suit, so we’ve also put together a list of folks who have done great work with customizations to The Events Calendar with information on how to hire them for help, if needed.
If you’re looking to change colors, then it’s worth noting that the WordPress Customizer can be used for this and without the need to open up a file.
Does this help answer your question? Please let me know. 🙂
Cheers!
Geoff