This mineral is often called potassium feldspar or K-feldspar, because by definition potassium always exceeds sodium in its formula. The formula is a blend ranging from all sodium (albite) to all potassium (microcline), but albite is also one endpoint in the plagioclase series so we classify albite as a plagioclase.
In the field, workers generally just write down "K-spar" and leave it at that until they can get to the laboratory. Alkali feldspar is generally white, buff or reddish and is not transparent, nor does it show the striations of plagioclase. A green feldspar is always microcline, the variety called amazonite.