I was too lazy to read the replies, so I don't know if this was suggested(highly doubt it though).
Paint a Y after the word Dell. You no longer have the Dell logo on it and instead have the word Delly. Its not a bad thing to have on your mouse. Besides, think of all the people that it will confuse when they try to use your computer. You could also paint an Alienhead over it, but then it would look like an alienware mouse...Painting a pot leaf over it prob wouldn't cover it well enough...If your lazy, a piece of electrical tape should be enough to cover it.