Hello HEMANG BHAVASAR,
Thank you for posting this question. There is not a specific color action that changes the color of text when a click occurs. Is there an issue with the text as it appears on screen? One other option would be to have an action open up a separate view based on the region selected and then format this differently.
If you have a Tableau workbook to share demonstrating the issue and maybe a picture or two to demonstrate how you think it might work better, this would help others to assist.
Best of luck