Diamond colour grades change in unexpectedly tiny increments.
Diamond colours range from D to Z, and as they trinkle down the alphabet the colour hue becomes more visibly prominent. Z is not a dark brown or yellow, yes, the colour is visible but far less pronounced than you would imagine.
Internet diamond colour-sheets aren't accurate. Just see them as a visual parable to just show that colour intensifies as you slide down to Z on the colour scale.
I can tell you right here before we sail off; G and H are white to any pair of eyes. You're better off focusing on some other characteristics like cut-grade and size when your in this boat.