A Star shaped brassia crossed with a solid purple miltonia should make for an easy growing purple flowering oncidium.
 
Growing  Conditions
Cool-intermediate Growing
Temperature 7-30 Deg
60% Shading
Grow in pots , mounted or baskets with Bark and Peat base medium 4-6mm
Plant size 30Cm
Inflorescence: (60cm)
NFS 10CM Pot