The seven spectral colours of the rainbow are: Red Orange Yellow Green Blue Indigo Violet

Cyan can be used, but blue-green would be more common in most cases. Cyan is usually reserved for the complementary color of red when describing light or printing colors.

Many say "cyan". Ed is right. It is a matter of scientific discussion. Newton defined that end of the spectrum as green, blue, indigo and violet. So Newton would say your "blue" is indigo and the colour between green and indigo is blue. Wikipedia has this to say: "According to Isaac Asimov, 'It is customary to list indigo as a color lying between blue and violet, but it has never seemed to me that indigo is worth the dignity of being considered a separate color. To my eyes it seems merely deep blue.' Today, the colour Newton associated as "light blue" (~520–490 nm / ~580–610 THz) is distinguished as a separate colour of either cyan or azure."

Unlike orange, which is a very ordinary, basic color word, there's no everyday word for the color between green and blue. There are, of course, hundreds of specialized color names. "Cyan" is a sort of a special case. It is a greenish blue, but In everyday life, people do not use it. I've never heard someone talk about a "cyan" dress, and even the biggest box of Crayolas does not include a "cyan" crayon. "Cyan" is a somewhat specialized technical name used in subtractive color printing (the process used for magazine illustrations). A computer screen works by adding light of three different colors: red, green, and blue. On a printed page, the printing inks are laid one on top of another and successively remove or "subtract" light. The traditional ink colors used in a common "four-color printing process" are cyan, magenta, yellow, and black, often referred to as CYMK. Cyan = green + blue, magenta = red + blue, yellow = red + green. If you "mix" cyan and yellow, by printing one on top of another, the cyan layer passes green and blue light but screens out red, while the yellow layer passes red and green light but screens out blue. The only color that pass through both layers is green. Thus, in subtractive color printing, cyan and yellow make green.

blue-green, teal , or turquoise are the common terms