Translation:The water is blue.
Just snooping around, but the first gets used more exclusively as a verb rather than an adjective (go yellow?), and though both can be bright the first gleams or stands out in some way, by contrast or like a highlighter or even honey?, whereas the second is described as the color of an egg yolk. The first or the other, sometimes both, are also described as golden yellow but this seems inconsistent . . .
It's a uniquely Korean thing too near as I can tell -- it's not coming across in the Sinitic, unlike blue-green or the strong color distinctions . . .
I found this explanation (파랗다 vs 푸르다),