El Capitan desktop icon not changing colour, for time machine disc

Hi

My Time Machine back-up hard drive's icon is usually blue but in El Capitan upgrade it stays yellow. I have renamed the disc, restarted the Mac.

Ejected the disc icon and in Time Machine preferences selected the disc, but still after it backs-up the drive it stays yellow. In Time Machine back-up discs preferences it shows the usual colour of blue but not on the desktop?