Alice, on the citrus spraying thing, you're right you probably would not want to eat fruit from that tree but only for the first year it was planted to allow the systemic pesticide to disperse. It's recommended to remove the fruit the first year anyway, so I think you really wouldn't lose out.
After that, though, you'd want to have a regular spray routine of soapy water or something just in case a citrus psyllid rode that far on a tree before it lunched on the neonicotinoid-treated sap.
Ken, on the sunburn thing, the red coloration actually goes away - the red turns green again - so it's not really permanent damage. A really sunburnt leaf has large brown areas that dry up and never go away.
