If it starts turning color,it's caramelizing. you've gone too far at that point. Imo,you'll loose some carbonation since some of the sugars will be converted to long chain sugar molecules that yeast can't matabolize. Next time,boil the water,remove from heat & stir in priming sugar. Cover & steep/let cool down while you prep the fermenter,etc. It'll stay clear & more fermentable that way.