Since Cristian's house has ten rooms, he painted 3/5*10 = <<3/5*10=6>>6 rooms with green color.
The number of rooms he painted with purple is 10-6 = <<10-6=4>>4 rooms.
Since each room in the house has eight walls, the number of walls painted purple is 8*4= <<8*4=32>>32.
#### 32