Yes. Colors that you would describe as red all have high values in the red channel, and small values in the green and blue channels. But those values need not all be strictly [255 0 0]. (Or [1 0 0], depending on the scaling you use.)
For example, using a [0,1] normalization...
img(:,:,1) = 1 - .2*rand(100,100);
img(:,:,2) = .2*rand(100,100);
img(:,:,3) = .2*rand(100,100);
You might reasonably call that entire image red, just various shades thereof. And the limits of what you might call red are probably subtly different for you than for me. The boundary of the set you would describe as red is indeed in that corner of the RGB color space though.