Can someone advise me on which bus/train to take from Kunming to Liuliang color sandforest, and how long is the bus/train ride?

There is only one train from KM to Liuliang and upon reaching Luliang, you may need to hire a local car to reach the Colored Sand Forest. The train takes about four hours.
Or you can take direct bus for Luliang from KM East Bus Station. The bus for Liuliang takes about two hours.