No doubt Lotus Notes email lost the battle to others very unfortunately (intentionally not mentioning the competitor names) for being the most popular email system. Perhaps this is the best what can be done in the current situation, start slowly changing yellow colors to some other colors (I wish it was not black though) which will not be associated with Lotus Notes nor Domino.
I really hope it will help to market the Domino/Notes application server platform to customers that have already moved off Notes platform and may reconsider it under the different packaging colors. I am and optimist and I hope it will help.