VisualStyleBuilder is a tool that is supposed to style in most cases colors, font-size, gradients. It is not recommended to change margin, padding and even borders which are considered as base styles that are building the controls layout. Any change of that styles could brake it. Even if we provide such tool and we have custom skin tutorial in our online help documentation, we do not support custom solutions. It is a developer/front-end developer responsibility to build the custom skin in a way that will not break the control.
Also note, that even the VisualStyleBuilder is a helpful tool, it could not substitute completely the Front-End Developer, it could help you to create easy and painless a custom skin based on any of the existing Telerik embedded skins, but if you like more customized solutions, it will be necessary to use both VisualStyleBuilder and handmade changes in an image editor software such as Adobe Photoshop and manually to change the base CSS file if it is necessary.
As for a detailed documentation, I think the video tutorials are more than enough as the VisualStyleBuilder has a simple navigation and options: Under colorize tab you could change the main colors/gradients in the sprite images. You have an option to use wen friendly colors with the web palette ColorPicker or RGB/HSV under HSV tab, and under Shift Colors tab you could change Hue/Saturation.
Under the other main tab - Fine Tune - you could change skin specific CSS options such as font-size properties, text color, background color, etc.
It is really simple and the video tutorials gives all the information that you need in order to operate with the tool.
All the best,
the Telerik team
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