Which of these Munsell soil designations is the reddest: 5R 6/4, 5R 5/2, 5R 7/3, 5R 6/3?
They are all the same hue, 5R, which is pretty close to a unique red. The second number is value, or lightness, and again they are about the same ranging from a middle lightness of 5 (half way perceptually between white and black) to slightly lighter at 7. The key number is the third one, chroma. A chroma of zero is a neutral gray and as the number increases the sample becomes more colorful. A chroma of 4 is significantly more colorful (more red in this case) than a chroma of 2. So, I would say that your 5R 6/4 sample is the reddest.
