gistfile1.txt

> db.xxx.insert({'colours':['red']})
> db.xxx.insert({'colours':['red']})
> db.xxx.insert({'colours':['blue']})
> db.xxx.insert({'colours':['blue', 'red']})
> db.xxx.insert({'colours':['green']})      
> db.xxx.find({ $or: [{"colours": {$in: ['red']}}}] }).count()
Wed Apr  9 15:47:41.383 SyntaxError: Unexpected token }
> db.xxx.find({ $or: [{"colours": {$in: ['red']}}] }).count() 
3
> db.xxx.find({ $or: [{"colours": {$in: ['blue']}}] }).count()
2

# This finds "document with any matching colour"
> db.xxx.find({ $or: [{"colours": {$in: ['blue']}}, {"colours": {$in: ['red']}}] }).count()  
4

# This finds "document which matches all colours"
> db.xxx.find({ $and: [{"colours": {$in: ['blue']}}, {"colours": {$in: ['red']}}] }).count()
1
> db.xxx.find({ $and: [{"colours": {$in: ['blue']}}, {"colours": {$in: ['red']}}, {"colours": {$in: ['purple']}}] }).count()
0