The English names for colors come from a variety of sources. My source for all this information is Wiktionary, the Wikipedia dictionary.
'Green' is from the Proto-Germanic 'groana,' which refers to plants becoming green or growing.
'Blue' is also Germanic, and apparently always referred to the color.
'Purple' comes from the Ancient Greek 'porphura,' the name of the shellfish that purple dye was made from.
'Red,' like blue, is Germanic and referred to the color.
'Orange' comes from the Arabic 'naranj,' the name for the fruit.
'Yellow' is of Germanic origin and referred to the color.
Is it a coincidence that all the primary colors have the same sort of origin? 'Black' and 'white' are also Germanic, one coming from a word meaning 'burnt' and one coming from a word meaning 'white.'