For the Mung Bean itself:
Brocho before eating this: Borei Pri Ha'adama
Brocho after eating the proper shiur of this: Borei Nefashos
For Mung Bean Sprouts:
Beracha before eating this: Shehakol Niyeh Bedvoro [others say Ha'adama]
Beracha after eating the proper shiur of this: Borei Nefashos
Source: Sefer Sharei Haberacha (5774, page 671, 673)