How do I get my calla lilly flowers to bloom in color?

I received a potted calla lilly plant at Christmas time. It had beautiful green leaves and colored flowers. Since then, the flowers bloom in green only. The plant looks healthy. And I water it regularly. I am not sure what fertilizer to use, however. Currently, I keep it on my porch to get partial sun. I live in warm, sunny, and humid Florida.How do I get my calla lilly flowers to bloom in color?
Use bonemeal in .25Cup or a ';flowering plant'; fertilizer mix, look for the phosphorous % number, it should be a little higher than the 1st number-phosphorous is the center #, the nitrogen is the first # this makes the plant green. www.gardensalive.com carries fertilizers that are organic, or you could go to KMart, Home Depot, etc. Also old fashioned callas flower only in white, but newer hybrids flower in pink, magenta, nearly black, yellow bordered with purple.