TextBlocks RGB CMYK HSL are cut when the style is extracted from blend. As a workaround use an implicit style approach. You can have folder with your XAML files and edit the Style of RadColorEditor in them. http://docs.telerik.com/devtools/wpf/styling-and-appearance/styling-apperance-implicit-styles-overview
when the slider of the LuminancePad is at its minimum or maximum the control visualized wrong color.