Try and mix it up a bit, and go crazy. Scary jumps at home help horses get used to scary comp jumps.
And you can add to them with simple things like fake flowers held upright in sand boxes, colored buckets as fill (not metal tho), tires cut in half, painted, and then sat beside the standard to form a wing ect. You can make some pretty awesome things from stuff laying around the yard, if you use your imagination. Just evaluate each peice of junk for ways it could cause injury, before use.
ETA - painted 44 gallon drums make good wings and fill as well.
Maybe someone can correct me on this but I've heard that horses see primary colour much easier than they do others. At the barn most of the jumps are white and black, red, blue, and yellow.
I don't remember where I heard so it may be a myth, anyone heard this theory??