There isn't much you can do except maybe introduce a new color to the plan and then draw it out on graph paper for placement. Short is short.
I would just play with the graph paper - you will come up with a great layout :)
If it were me - I'd add the green since the print you have is dark with a lot of green. I think the other two colors will be too bright and detract from the print... but then I'd also use black fabric instead of muslin. I walk to a different beat. ;)