An update for xScope is now available in the Mac App Store and through the in-app update. xScope 4.2 features a new setting in General preferences that allows tool windows to stay in the Space where they were activated. If you do design or development in one space and email or chat in another this will come in very handy.
In addition the Loupe now features a new eyedropper icon that allows you to quickly switch the working color space as well as a new preference to highlight colors that are out of gamut. Version 4.2 also fixes a number of bugs like truncated color values in the Loupe, an improved layout of Dimensions controls in El Capitan and a host of others.
This is a free update for current users and is available now. Check your updates at the Mac App Store or, if you purchased from the website, check for updates under the xScope menu item.