finderfoldersmacos
I use Finder with the 'view as list' setting. Today I noticed that one of my folders had a darker grey arrow next to it than all the others:
(The notes folder is the one with the darker arrow)
I then took a copy of the folder to see if the copy would also have the dark arrow, but it jumped to a different folder! (now tests_and_trials)
I closed and reopened the finder window, and all the arrows were light grey with no dark grey arrows at all.
What was going on?
(This is on OS X 10.9)
It just changes pages on the icon preview for multi-page documents.
Not spectacularly useful with small icons like that, but if you have huge icons set or are in column or cover-flow view, it's a quick way to see what's actually in the document without opening them.
If you click away from the icon, it goes back to the first page, so it doesn't actually change anything.
Okay, so I just found a work around instead of a solution..
Made a new folder, changed background image and dragged everything over..
Thanks for the suggestion, I'm sure it would have worked but it seemed like a lot to try just to change the background on a folder.. A pretty pointless thing anyway really!
Best Answer
This is simply a glitch. The darkened triangle is used when the button is pressed. It doesn't mean anything about the folder and will be fixed by closing and re-opening the window as you discovered.