ColorTag is a powerful API for color detection. Taking an image file (or URL) as input ColorTag produces a list of text labels and hex RGB values that can be then used as tags for a certain image or item. Check out visual demo here: http://apicloud.me/apis/colortag/demo/. The API can sort tags by relevance (detecting colors of objects on the image, e.g. a dress, a car, etc.) or simply by weight in the image. First mode is perfect for e-commerce applications, allowing to automatically tag items with colors by simply providing a photo or a thumbnail and build a color tag cloud, so users are able to search items by color (e.g. red). Weight sorting mode can be useful for photos, wallpapers or other images without well-defined objects on them to analyze the palette in general. Text color labels can be assigned with different precision (just basic colors, W3C-compatible colors, precise colors, etc.).