In many languages blue and green are considered to be different shades of the same color. In English, that color is referred to as 'grue'
According to Brent Berlin and Paul Kay's 1969 study 'Basic Color Terms: Their Universality and Evolution', distinct terms for brown, purple, pink, orange and grey will not emerge in a language until the language has made a distinction between green and blue.
Many languages, however, do not differentiate between certain colors on the visible spectrum and they therefore do not have separate terms for blue and green. Instead, they use one term to cover the description of both these colors. In English linguistic terms, this cover description is referred to as 'grue'.
For example, in Vietnamese the word to describe the color of both tree leaves and the sky is 'xanh'. To distinguish, they use xanh l cy ("leaf grue") for green and xanh dương ("ocean grue") for blue.
In the Thai language 'khiaw' means green, but when referring to the sky or the ocean, it means blue. In Chinese has 'qīng' can refer to green, blue and sometimes even black! The Korean 'pureuda' can mean either green or blue. Many African languages also utilize the same word to describe both colors.
But what is the color of water? Many will say blue, and some of us will say green. Color is sometimes in the eye of the beholder.