Actually I heard the multicoloured logo of Google was unintentional, when it was in their early days they got someone to re-design the logo and they just wanted to see the colour range on the logo (restricted by technology back then) and they decided it looked good with all the colours. If you dig around you will find the original logo was just blue.
Based on wiki Google is known for its relaxed corporate culture, of which its playful variations on its own corporate logo are an indicator. Check out this if you want google
Also colors have effects on people.. I try to use this when I am designing sites.. or even at my office and home..
sergey designed it. it cost him nothing. so anyone who think u need to spend big money on a logo is dreaming.
Blue = Water Red = Fire Green - Life on Earth Yellow - Sun The message is clear , there is no life without water , fire , sun! Also , there is no life without Google (Damn , I hope Sergey won't deduct any $$$ from my salary for exposing his mystery)