Best way to do that is get white letter tires. Seriously though...like you, I like white letter tires, especially on my motorcycle (yes, that's a pen in the top photo...before and after after one day). But, as soon as the tire warms up, the appearance changes. The white cracks, fades, flakes off, looks grimy, etc. I have tried several different pens from the "tire" pens at AutoZone to acrylic pens from crafts shops. They all suck to about the same factor. Regardless, none of the IMO, would give you a quality look that you're after. My opinion...learn to like black walls or find something else.
Don't know why GY is sooo goofy about that. And with the Duratrac, I don't know why they don't put black on one side and white on the other...it's not an asymmetric tire like my MTR that you can't turn around.