I downloaded an icon from Icons8. With their tool I recolored it to dark blue (#2c3e50). After unpacking and uploading the 48px icon I got the following result:

As you can see the color is not #2c3e50, but #738697. I was quite confused, so I opened the file with different programs (all using Windows 8.1):
Paint.NET: #2c3e50
Paint: #2c3e50
Gimp: #2c3e50
IrfanView: #2c3e50
Chrome: #738697
Firefox: #738697
Windows Picture Viewer: #738697
Does anybody knows what's going on here?