Hello, Hokaplan, I feel the appearance of color in a diamond is subjective to the eye of the beholder. However, color grading does affect the cost of a diamond, for sure, but if a stone is very very well cut ( and I'm talking of the round brilliant cut ) it will appear whiter as more light will be returned to the eye.
*And remember, color grading in round brilliants is done from the back. We, as consumers view color from the top.*
For example, I have two diamonds. One is an E color grade and is an ideal cut Lazare Kaplan.
The other is an I color grade and is a Hearts on Fire branded stone.
Although the E graded Kaplan is the higher color grade, it does not appear as white as the I graded Hearts on Fire when I hold both stones side by side.
The Kaplan is a beautiful stone, certainly, and it's my favorite, however, the lower color I graded Hearts on Fire looks whiter when held next to the Kaplan, side by side.
I would have never believed it had I not owned both stones. For years, in fact over 100 years, Lazare Kaplan was thought by many to be the industry standard for ideal cutting and is still highly respected.
At the end of the day color importance depends on you. If you like the way your stone looks, then, keep it. Sparkly and bright is pretty desirable in diamonds and yours sounds lovely.
You will pay more for a whiter color graded stone, but, the appearance of color has so much to do with how well it is cut.