Why did people name the orange an orange but a banana not yellow or a apple red or a cucumber green?

English speakers actually used the word orange to describe the color after the word orange, or naranj, became integrated into the English language. The naranj is an Arabic word for the citrus fruit that found favor on trade routes. English speakers dropped the first letter "n" in common reference to the naranj fruit sometime after the Norman conquest (around the same time the "n" was dropped from napron to become apron).

Prior to the commonly understood reference of the color of the naranj fruit, the word ġeolurēad (literally "yellow-red") was used to reference the color English speakers understand as the color orange.

The Old English word geolu, or geolwe refers to yellow as a "color," but the word banana is a word borrowed from Portuguese that references the fruit grown originally in West Africa. Although written documentation of this adoption is not extant, more than likely the Portuguese borrowed the word banana from the West African cultivators of the plant.

With consideration of the actual pattern of language dispersal, the question should logically be "if orange is derived from an orange why isn't yellow called banana?" and the answer to that question is that there was a perfectly understood word for yellow in the English language.