interpret the following C#.NET code related with RGB

this code is for skin color segmentation in C#.NET, please tell me what is difference bet R & r

color = bm.GetPixel(i, j); 
r = Convert.ToDouble(color.R) / Convert.ToDouble(color.R + color.G + color.B); 
g = Convert.ToDouble(color.G) / Convert.ToDouble(color.R + color.G + color.B);

f_upper = -1.3767 * r * r + 1.0743 * r + 0.1452;
f_lower = -0.776 * r * r + 0.5601 * r + 0.1766;

Answer 1

[Walter Roberson]

"r", "g", and "b" are relative color values. I do not remember the proper technical term. The effect is to correct for illumination.