Is there any way to change colour before and after one module ends in a course in storyline?

Sana, you can do this by using separate text box entries, instead of a single bulleted paragraph, and creating a variable that triggers when the learner has clicked on the item. I would use a state on each text box entry that changes to "visited" when the variable (for example, "module_complete") is true. It should be fairly easy to set up.

Good luck!

JoeH