The so called "Red form" is given to any almost solid to solid red colored Phal. cornu-cervi. This includes, f. chattaladae, f. saguinea also known as var. rubescens, f. thalebanii (no yellow backgrownd color but just white base color) or just heavily marked Phal. cornu-cervi. Unfortunately, sellers use this generic term to sell their plants. See below some or the forms but I don't have a picture of f. thalebanii but here is a link
http://www.orchidspecies.com/orphotdir/phalthalebanii.jpg. I hope this helps.
Ramon
Thanks Ramon.
One may not get what you have paid if a Red Form is passed on as f. chattaladae.