Translation:She has blue eyes.
蓝色的眼睛 is literally "blue colored eye/s" (btw, not accepted here - reported. Most ppl would say blue eyes or blue eyed but "he has blue colored eyes" is perfectly valid.
一双绿眼睛 is "a pair of green eyes", not that common but plausible if you want to emphasise both eyes.
Both are ok. You could also have both in the same sentence, it's not a matter of choice between one or the other: 你有一双蓝色的眼睛. You could also remove them both: 你有蓝眼睛. Usually in a language, the more you add words, the more it sounds formal or childish, whereas shorter sentences are closer to everyday speech which strives to convey more ideas as fast as possible. It's not always the case, but most of the time that's how a language works. We'd need a native to confirm which version is the most common in everyday speech.