What do the shapes and colors in Tlingit art represent?

This question is not properly framed. The various forms in Tlingit design, contextualized, do not mean anything. It is when these forms come together that they take on the familiar shapes of crests (animals, forces of nature, geographic features, etc). The primary shapes are ovoid, u-form, split u, trigon, and s shape. The underlying concept of how these things should be put together is called form line, a term coined by art historian Bill Holm in the 1960s. The representation comes from the final product, be it Thunderbird, Bear, Killer Whale, or Raven. Standing alone, the shapes are meaningless. The characteristic colors of Tlingit art are blue/green, red, and black. These colors are derivative of natural pigments and materials that were available to the ancient Tlingit, and continue to be the dominant colors in the art today. Black is generally used for the primary form line, red for the secondary form line (though this can be reversed), and blue/green for the tertiary (filler) areas of ovoids. The colors do not seemingly have any spiritual significance, beyond being viewed as traditional due to their origin from Tlingit lands and their continued use for at least the last several centuries.