def valid_color(value)
          ok_color_names = %i(black silver gray white maroon red purple fuchsia green lime olive yellow navy blue teal aqua)
          valid_hex = /#[0-9a-f]{6}/i
          valid_palette_entry = /^\w+(?:\s\[[0-9]+\])?$/
          message = "Invalid color. Please specify a color name, a hex value (with #), or a palette entry."