What is the context of the 'W' value in a RGBAW as it pertains to a ColorMatrix?

Question

I understand that matrix[0-3] values are the RGBA values for R', but the only description I have been able to find for the matrix[4], 'W' value is that it's used as a placeholder. Can anyone provide any context as to how the "placeholder" 'W' value would be used?

float[] matrix = {
            1, 0, 0, 0, 0,
            0, 1, 0, 0, 0,
            0, 0, 1, 0, 0,
            0, 0, 0, 1, 0,
    };

Best,
Austin

Answer 1

Base on this site RGBAW stands for Red Green Blue Amber White.

According to this site:

What Is RGBAW?

RGBAW refers to the design of the LED matrix that drives the Luxli lights, and it's 
what separates the Timpani from most other 1x1 lighting solutions. LED panels of yore 
usually had one of two different LED colors, either daylight balanced or tungsten 
balanced, or a combination of the two, for bicolor operation. RGBAW combines five 
different diodes (Red, Green, Blue, Amber, and White) to pump out nearly any hue on 
the color wheel by mixing the output of these diodes. Importantly, the RGBAW matrix 
doesn't take away from the Timpani's ability to operate as a standard bicolor panel. 
But what fun would that be when you have so much more under the hood?

Answer 2

The full color matrix is actually 5x5 rather than 4x5. The fifth column is indeed a placeholder, and it doesn't do anything. The fifth row, however, represents a translation of the RGBA columns. See here for more details.