How do you hide url text? I make it white when background is white, but result is deep black. Make it gray, result is the same.. When I customize adsense block I am shown invisible url text, but when I place it on the site it becomes dark.
You can't. The AdSense code will automatically choose a color that contrasts with the background color so that the URL is always visible, no matter what you do. The only way to avoid showing the URL is to use a format that doesn't have the URL in it, like the half-banner format.
You can certainly make it lighter, yes, but you can never make it completely go away. When it starts to get too light, Google will just force it to a darker color. You have to live with it or else switch to the no-url formats.