How do brands choose the color to represent and distinguish themselves?

Here is a cool poster from COLOURlovers showing how the major brands of the world are covering the entire rainbow spectrum. Looks like blue and its variations are favored the most among the brand community followed by red and its variants. Another interesting fact is that the many of the biggest companies use multicolor logs with Google, Picasa and E-Bay included.

Also see - Psycology of Color.