Thanks for the heads up on the questions. I set up the imgur account yesterday and need to migrate some of the stuff from photobucket, etc to the more friendly host service.
In regards to the color and toxicity, Proposition 65. Lead, cadmium, other metals used to pigment and assist with the porcelain enamel finish were outlawed due to handling and use during the manufacturing process and some follow on.
Now your house may have lead paint and your kids school may have asbestos here and there. But as long as it's encased and not disturbed, you should be alright.
I don't recall any "hard evidence" to not using a vintage grill for outright cooking. Maybe some fumes are toxic, but how much? You may not want to scratch at it or eat or lick the finish any more than a vintage car or your childhood bedroom from 1956. I haven't used the red gumball in years and years.
Remember that grilling in itself is packed with carcinogens. I read where you shouldn't cook with aluminum foil, but once or three times a week I ball up some green peppers and onions and toss them on the grate. I have a brass fitting on the end of my garden hose and when I'm done rinsing the lawn mower, I take a drink.
I don't feel I'm really answering the question with FACT other than it was definitely present in manufacturing. And the Stephens family seemed annoyed they had to drop some successful colors and options..