An example and the difference between RGB color and RGBA color!
RGB values go from 0-255, resulting in 16777216/256 x 256 x 256) colors.
The so-called alpha value describes the transparency or permeability of the pixel.
Example RGBA 255 , 0.0, 127 would be the color red, which is 50% permeable, transparent or transparent
R = red G = green B = blue A = alpha
It doesn't matter how it is written! The main thing is to interpret it in the correct order.
Here is an example of how a transparent desktop clock looks on the desktop with the same color and a different alpha value. 0, 75%, 25%
You can see exactly how the alpha value affects the appearance, it is almost like reducing the RGB values, which is also mathematically correct, only that the background also is added with the corresponding share!
75% alpha means that the background gains 25% in importance!
Or rather, the front texture 75% mixed with 25% background.