Just as example, but I've tested it with various designs and colours.
/give @p minecraft:banner 1 0 {BlockEntityTag:{Base:2,Patterns:[{Pattern:cbo,Color:12},{Pattern:bts,Color:15}]}}
Why would this be as intended? If it is working as it's supposed to, rather than being a bug, then I recommend a change.
Seems to be resolved as of pre-release 3