how to add colors without using the template for tables

Luscious1    (That's quite a user name you've chosen)

OK. Shouldn't need to scream here, but yes, Excel could be compared to a large chain saw that can work a lot of havoc in an instant used by a novice.

Take a deep breath. There are ways to approach it--and, to put it all in perspective, Excel never itself causes the spilling of blood. Never. It can undo a lot of work, so here right off the bat are two ways at least to minimize that likelihood.

1. Acquaint yourself with the "Undo" button, already mentioned by PeterBartholomew1 . It's the little left-pointing arrow with a tail, up top on the green tool bar at the very top of the Excel window. Or available as a menu selection under the main Edit menu
2. Make a copy of your file BEFORE doing anything you're worried about. Back to the main menu again, use File....Save As or Save a Copy. That way, IF a disaster should happen, you'd have a back-up copy and could just carry on.

Whew!

OK, now to your worry. Creating your data set as a table--I assume you're talking of doing it through the Insert tool bar, where you just click on the "Table" icon--is NOT going to delete your data at all. It will set your rows to alternating colors and highlight the header row but lo and behold, leave the text and number entries as they were. And believe me, as you move on and learn the power of Tables, you're going to be grateful that you set it up that way.

Here is a link that you can study quickly so that you can approach the task with more confidence.

https://exceljet.net/excel-tables

There are also a number of YouTube videos--just search for "Excel Tables" to find them.