Check out Pigment by Shapefactory
One of the most important and easily underrated aspects of a website--or any visual medium--is the use of color. For anyone that's attempted to read yellow text on a stark white background or dark brown text on a black background, the reasons for this are already apparent. For those fortunate enough to have avoided drastic misuses of a color palette, it is hard to explain just how much of a negative impact choices like these has on user experience.
One of the best ways to guard against making errors when choosing colors is to compare different sets via a color palette. These tools remove the necessity of training in color theory or experience in comparing and contrasting color choices. ShapeFactory offers an incredibly simple, single page color chooser that presents an exceptionally large number of groupings to assist users in the process. The main area of the page consists of squares with a circle in its center. Both shapes are a different color and each color has four different shades that change with a click. The hexadecimal code for each chosen color is prominently presented to ensure identical colors appear in all uses. Each square also includes a small heart in the top left corner to create a "favorites" group. This group helps users focus on making decisions for a larger number of colors without having excess choices on the same screen.
A sidebar on the left of the screen provides several controls for the page as a whole. Users may adjust the pigment of the page which changes colors from richer tones to a more pastel-type saturation. There is also a lighting control that adjusts the brightness and darkness of each color on the screen. Changes to the colors are reflected instantaneously in their hex color code which avoids noting the wrong code for any color. Users may also pare down the overall palette square to a specific color for more precise tuning. The sidebar also provides quick access to any "favorited" palette squares. Pigment by Shapefactory is a simple tool that earns its place on a bookmarks bar.