The maple leaves are just changing color to yellow and red.
The pictures below were taken around 'Kogen Eki' of Beppu Ropeway (altitude 500 meters).
Now is a good time to see the foliage at the top of Mt. Tsurumi (altitude 1375 meters), around 'Sanjyo Eki' of Beppu Ropeway. The leaves of lower altitudes are about begin to change color.
FTIO offices offer you information about how to get Lake Shidaka and Beppu Ropeway.