Jimi Hendrix, a self-taught musician, was unable to read music, and as such often experienced musical and emotional ideas in terms of color (similar to the condition of synesthesia). The lyrics reflect this (Hendrix stated, in explanation of his color-emotion interpretations, "Jealousy is purple; I'm purple with rage...", paralleling the lyrical reference to the "purple armor" of a personified anger). The piece also has elements of a love song, as Hendrix explained that his usage of color is how "... you explain your different emotions in colors toward this certain girl who has all the colors in the world...".
This song discusses many colors: "In shiny metallic purple armor; fiery green gown sneers at the grassy ground." Because of Hendrix' inability to read music, he would often describe emotions (and music) in colors rather than more descriptive words. Jimi was a very emotional and colorful person, and in this song he really brought out his emotions in a wild imagery that at first glance can be easily misinterpreted.
This follows the trend of Jimi's work, as it was another sad emotional song.
The line "My Yellow is this case is Not so Mellow" is a reference to the Donovan song "Mellow Yellow" and describes Hendrix' inability to express his feelings to a former girlfriend in any conventional way. So Hendrix used colors to describe his feelings of fright, uncertainty and frustration. It's that frustration that leads him to say at the end of the song: "And all of these emotions of mine is holding me from giving my life to a Rainbow like you."
wikipedia & songfacts.com
