There is a blue light icon below any open programs on Plank. I have disabled the function to have icons on plank that are not pinned to it, but the blue light persists on icons that are pinned. I haven't found any answers on how to get rid of it.
SnapOverflow
I found an answer to my own question by looking into the source code of Plank. I'll post my answers here so if anyone else would like to get rid of the running app indicator, they'll be able to. First I gave myself root by entering:
and I entered in my password to gain root privileges. I then entered
You don't have to put "Transparent," that's just the theme I'm using. If you're not using transparent, then insert whatever theme you're using. From here, a text editor will pop up, and you will be allowed to edit it. If there is already a value for IndicatorSize, replace the value with 0. If there is not, then type in
on a new line. Now, all you will have to do is hit ctrl+s, and your running application indicators will be no more!