I've never had that charger brand. However, with most of my chargers, the indicators are fairly predictable. If you plug in the charger with no battery, its job is finished, so it lights green. If you then insert one or more batteries to be charged, its job is unfinished, so it lights red. Once the charging is done, it lights green.
One weird charger I had would light up red and green at the same time, and it was failed.