Two basic color words for different types of blue. You might think of azure, cobalt, and sapphire as shades of blue. To a Russian speaker, синий and голубой are not shades of each other, they are different basic colors, like blue and green in English. And there is no one color word in Russian encompassing all blues.
I think pink is less clearly a shade of red (it can go a bit into blue), while "голубой" is simply light or pale blue: AFAICT it's used as an alias, and one may call it "light blue" as well.