Earlier, Nokia had introduced Nokia X series (Nokia X, Nokia X+, Nokia XL) smartphones those run on Android OS. Nokia X series smartphones are a customized form of Android OS. Last month Microsoft bought Nokia X2, an upper version of previous X series smartphones.
However, so far Nokia hasn’t launched any Android based Lumia smartphone. But if @eveleaks report is true, then Android based colorful Lumia smartphones are not far away. Recently Microsoft updated Windows 8 OS to Windows 8.1 OS. Analysts say that Windows 8.1 has reduced difference from Android OS.