Once it's a ways away all underside surfaces are 'shadowed and look black'. In close....doesn't matter quite as much. What you want is dramatic differences between the top and bottom. Red becomes black at distance in shadow. It seems like a great choice but isn't. Some of the florescents can show up quite well. Which ones seems to be a matter of cones-n-rods in the eye of the beholder sort of thing. Some like yellow, some green, some pink, some chartreuse. Any/all can work. Use what works for you.
Paint adds weight if used indiscriminately, especially on the tail. I suggest you invest in some of this tape and make some dramatic black stripes on the wing bottom, or purple, or orange, etc. Something that stands out. Stripes stand out more than solid color.
2" Acrylic Colored Carton Sealing Tape
Then make whatever top colors suit you. The tape can be removed if needed AND will add strength. Paint just adds weight.
Z-foam is somewhat 'greasy'. Good stuff and resistant to impact but is hard to paint without flaking off. Taping it is easier and more reliable. But GOOD taping is an acquired art.