a step wise gradient of colors;

a series of windows in the surface, each window in the series bordered by one of the colors, and each window including a transparent portion in the plate, and

a back plate including, a lip protruding from a surface of the back plate at an outer edge of the back plate, and a series of transparent protrusions in a center area and protruding in the same direction as the lip;

a middle layer including the color gradient, the lighting indicator, and a series of through holes, each through hole bordering each one of the transparent protrusions and defining one of the windows, and wherein a first surface of the lip borders an edge of the middle layer;

a cover plate comprising a transparent material for viewing of the color gradient and the lighting indicator, and for viewing through the plate at positions corresponding to the transparent protrusions on the back plate; and

wherein a second surface of the lip is coupled to a surface of the cover plate and provides a waterproof seal;

(i) the icterometer comprises a lighting indicator configured to indicate the quality of lighting; and/or

(ii) the plate is waterproof and inert to cleaning solutions applied to an external surface.