color didn't take but....

Hi--I colored my half inch of hair about two weeks ago (I also have been on herceptin since late August; stopped chemo in late October). My color is a reddish blonde. The color is different from before (same manufacturer, same color) but I thought a bit brighter than before. Are you sure they mixed the same colors together? Also, in the past you were probably just doing the roots but may not have noticed the roots were somewhat darker than the rest of your hair. Perhaps the next time.