I always thought the nicer the colour,the better the quality. Turns out that since the orange is sometimes dyed with food colouring, you can’t count on that to choose your oranges.
You’re actually supposed to look for brown spots on the skin because they indicate a good quality orange. You should pick a sweet orange by examining the navel (the belly button of the orange). Choose the ones with the biggest holes.
Hope this helps you pick better oranges! :)