Wikpedia says “We ended up with the primary colors, but instead of having the pattern go in order, we put a secondary color on the L, which brought back the idea that Google doesn’t follow the rules.”
I dunno on the orange/yellow debate. Using GIMP to check the hue value, I get 41, which is closer to “orange” than “yellow”. Finally, an excuse to break out that “macaroni and cheese” crayon! 
Depends what part of the letter you are sampling from. It has varying degrees of specularity, as all the letters are shaded. Although there are orange-ish hues in it, I interpret that as a result of the shading and the original letter as basically yellow.
I just checked again, and while I can see a very small amount of yellow in the “o”, it is overall much more orange than yellow. And my monitor settings seem fine as I can see yellow elsewhere.
Well as chaoticbear’s quote above proves, Google themselves consider it yellow since orange is not a primary color.
I think the “l” is green. That’s about it.
If I go to Google images and google “Google” I see plenty of their logos with a clearly yellow second “o” and it looks quite familiar to me, but it is not even close to the clearly orange letter on their actual page that I bring up. Again, anyone else?
From memory: colors? there are colors?
I dunno. I took 5 or 6 samples from around various parts of the letter, and although the other values changed, the hue stayed constant. ::shrug::
The same wikipedia article also mentions an update of the logo in 2010, updating the color as well. You can compare it to the original on the same page. It is indeed oranger, but i don’t know if we can objectively call it one or the other.
Let’s just agree on yellow-orange, then, okay? I think I have a crayon that color.