I'm not sure what info you need, but it has an interesting history. The concept for Southwest started in the late '60s and after a lot of wrangling SW finally got going in 1971 or 72 with a handful of routes. You may wonder what this tidbit has to do with colors, but Texas Intl. and Braniff, who basically had monopolies on certain segments of thje Lone Star State, gave SW a really hard time, and things went to court in order to get SW started. Anyhow, as part of the settlement, Braniff had to supply paint to SW. The colors SW uses -- an ochre, orange and red -- were originally the same ochre, red, and orange that BN used in its pastel schemes of the late 1960s. Over the years, SW has varied the shades, especially the ochre, but the idea is the same.
SW is aware that the scheme looks a bit dated (it's not horrid, but certainly is a relic of the 70s) but they feel it is extremely identifiable with their product, so they are reluctant to change it.
CV990, the Maserati of the skies!