Right now there's no support for scrolling widgets in the MIUI Launcher. If you want to use Colorize Widget, you'll have to use ADW.Launcher, LiveHome, OpenHome or Go Launcher.
That's the one thing I don't like about MIUI, because it's quite a nice feature for a social feed or agenda widget. If you would like to see this feature in upcoming releases you should post a suggestion into the MIUI Guestbook or their Facebook page. The more people ask about this, the more likely they will add support for scrolling widgets if possible
The best solution I've found to this is to install an alternate launcher ( I used Go Launcher ), and put a shortcut in the MIUI launcher bar. Then I put all my scrollable widgets on the Go Launcher screens, and kept the 'Home' button mapped to the MIUI launcher. So it's quick and easy to flip between the MIUI and Go Launcher desktops, and I get the best of both worlds