This is going to sound crazy but here is my answer (depending on how deep your background fabric is of course). As brown has an orange pigment in it's production and blue is opposite to orange on the colour wheel, (and the opposite to green is red which is next door to orange) it makes supreme sense to me to use some orange as perhaps the centre of your middle panel. You can always use a mixture of the blue/green/brown in the surrounds of the dresden plate. It will make both colours "pop"!
Therese