For the device to work properly, we must calibrate it, because both the parameters of the LEDs in the WS2812, the magnitude of the supply voltage, and the geometry of the holder of light and photo diodes can differ. Ideally, you need to use a ready-made template (Fig. 1), but we decided to develop a set of colors ourselves and print it on a color printer. To do this, we used a spreadsheet program. In spreadsheets, we can set the RGB color {Red, Green, Blue} of a specific cell (i, j) using the command

Cells(i, j).Interior.Color = RGB(Red; Green; Blue) 

We made two reference color sets - for 27 and 64 colors, respectively for each component from the set {0, 127, 255} and {0, 85, 170, 255}. An example is shown in Fig. 2.

Fig.1 Etalone color set

Fig.2 Self-made color set