What does the vector length of a rgb color in vector space mean

Question

I'm working with raw camera data where the color values are in full float. In RGB space represented as 3D cartesian coordinate, every color can be plotted as a vector in the positive x,y,z coordinates. What does the magnitude, or the length of the vector represent? Originally I interpreted as intensity or luminance of the color value. But I'm getting confused over another concept, which is the sum of all 3 colors component. So what does the sum of all 3 color components represent and what does the vector length of the RGB vector represent?