How do I implement a color change for Items clicked on in Gallery Categories List?

Hello!

I would like a color change to occur for Gallery Items in Categories List of which I (and/or members) have clicked on as I go down through the list.

My Gallery Categories Listing is quite extensive, so it would be beneficial to have an item (and sub-item) to change color once it has been clicked on.

Currently:

All Categories viewed (not yet clicked on) are in BLUE. That's OK.

When a specific Category Item is clicked on, the color changes to RED. That's OK

However clicking on a second or third item (or more), the item previously clicked on returns to BLUE.

Instead of the item returning back to Blue, I would like it to be a third color, perhaps GREEN.

After the person viewing the Gallery Items List in Categories, and going on to something else - then coming back Gallery - all the original color designation

would return to what is shown in the above first two lines of text under "Currently".

In a previous forum (using Woltlab Software) I had such a color configuration properly working as described above.

I think the person who set it up for me was Ramiru - (hope I have spelled the name correctly).

Unfortunately I lost the CSS settings when my previous computer went "bye bye".

So now I have to have someone help me re-establish the proper CSS Code for me.

DJ