This is the 7385th most frequent Russian word.
голубой
Light blue.
In this sentence, 'голубое' is an adjective describing the noun 'небо', referring to its light-blue color.
Я люблю смотреть на голубое небо.
I love watching the blue sky.
Here, 'голубую' matches the feminine noun 'рубашку', describing its color.
Этот мужчина носит голубую рубашку.
This man is wearing a light-blue shirt.
In this case, 'голубое' modifies the neuter noun 'озеро', expressing its blue hue.