Hi. I'm a jeweler, full time with a jewelry store I've had for 20 years. Each color is a range. A spectrum. In other words, there's a whiter F and an F with more color. A whiter G and a G with more color, etc.
You may have an F color, that's technically an F, but is it an F that's almost into the G territory. Then what?
Never buy a piece of paper and pick each diamond on its own merit. You may find that if you go with the F color, it may not be as pretty a stone as your G diamond. All F VVS1 stones do not look the same, even of they are graded the same. Sometimes I get 6 diamonds in for my clients and tell the client we are going to look at the diamonds first, and that I will reveal the color and clarity at the end. Many times they are surprised that they fell in love with a diamond they did not set out to consider, color or clarity wise.
There is a huuuge scandal waiting to come, about GIA diamonds graded in India being way undergraded, for instance. The general public doesn't even know about this, and probably won't for some time. GIA is denying this fact, however us jeweler's are seeing that the diamonds coming out of India are overgraded, sadly. So where will that leave you, if you pick such a diamond? The cheapest 1/3 diamonds on BLUE NIKE are all from India. All these innocent buyers ending up woth diamonds that are actually lower in color and clarity.
My point is: Be happy if your diamond is beautiful. There is literally ZERO guarantee an F color diamond of the same proportions is going to be p-r-e-t-t-i-e-r. You may end up with yellower F and you may currently own a whiter G.
Always buy with your eyes, and never, ever a piece of paper.
Inbox me if you or anyone else has further questions I can help with!
Sherry