I believe you can assign a class to text (a bit like CSS) so you can make changes like this in one go...
They're called paragraph styles and using them is definitely one of the 10 Indesign commandments! Maybe the 1st one ^^ (see https://helpx.adobe.com/indesign/using/paragraph-character-styles.html)
Anyway, since you haven't used them, you can use the Find/Replace feature to apply one.
Question is: what is common to all your texts? Color maybe?
Let's imagine you got black text and you want it blue.
Use the Find/Replace feature to "catch" all black text and... change it to blue?
Possible but... nooo!!! Apply a paragraph style (set to blue text) instead...
See example below. Of course, in my example, all black text will be changed, so you have to figure out what specs make your text unique. Could be a combination of many things (color, font size, font name, etc...)