Grayscale is used with one primary branding color, OR a more complicated color palette is attempted with too many colors or with colors which are unlikely to work well together.
The color palette has a limited number of colors, including more active and more neutral colors, which are chosen to work well together.
The color palette has an extended range, with variations on colors for different contexts, such as rules, text, or surface areas. In addition to dominant primary and secondary colors, select supporting colors are available for added expressivity.
The color palette creates a strong brand voice, with consideration for how the color palette helps position and differentiate the product within its market.