I wondered the same about the coloration until I saw others' pics that looked similar for those varieties. Marco Island is right off the coast of Naples FL (near Ft. Myers). My yard is completely sand... not a spec of real soil and the trees seem to be doing great. The Glenn and VP were planted 2 years ago, the others were planted last summer. All young, but seem to be fruiting well (if they hold on). Luckily I'm supplemented by a neighbor with a 25 year old unknown variety mango that is completely purple and just fantastic. I'll post some pics of that when I get a chance to see if others can determine the type.
Just when I thought I was happy with my collection - I'm dead set on adding an Angie, Maha, and Lemon Zest. More than likely will swap out the dying Tebow.
- Brett