I was searching a lot of information about Color Space and how can I prove that the RGB color space is or not Orthogonal Transform, I suppose that it's Orthogonal Transform because all the image of this color space that I saw, it show like a cube, but I found in Wikipedia that I can express any color space with the reference standard CIE-XYZ and I found here the matrix transform for this two space here but those matrix are not Orthogonal, so I don't know how is the correct answer.
Thank you for your help.