Where Would You Think

the hard boiled one would be whiteish while the unboiled would be lighter.

Not quite. There is a much better way, which does not depend on the colour of the eggs...

spin them, the hard boiled egg should spin faster than the uncooked one because of the free spinning yolk in the middle.

you could shake the eggs up and find it out from the sounds produced by them!hard boiled will not produce any sound!!whereas the uncooked one will!!

Not quite (ever tried listening to an egg whilst you shake it?). There is a better idea, and the spinning suggestiong is very, very, close.

Start each egg spinning quickly on a flat surface~
Momentarily press down on the top of each egg with your finger to stop them from spinning~
If the egg is hardboiled, then after stopping it it will stay still~
If the egg isn't hardboiled, the yolk in the egg will still be spinning and, as such, once removing your finger the egg should begin spinning again~
Theoretically. :)