Change D's brand color to blue.

[Jan Hönig]

I think the color red is fine. It sands out and feels nice and 
warm.

If you want do marketing and be creative then invent a proper 
mascot.
Something which can be made out of plush so you can hand them out 
at conferences.
I got a chameleon from SUSE. I don't even like SUSE. But it is a 
nice plush toy and it is a good remainder that it exists.

SUSE chameleon: 
https://suseus.quickorder.uk.com/products/name/small-suse-chameleon/product_id/5500266000108?size=&start=

Common Lisp mascot: 
http://missingfaktor.blogspot.com/2012/07/tour-through-land-of-lisp.html
http://www.lisperati.com/lisplogo_warning2_256.png