Sodium Citrate - Produces a neutral-toned print. Not quite as warm as Potassium Oxalate, and not as cool toned as Ammonium Citrate.
Ammonium Citrate - Produces a cool, black toned image. Replace often in order to maintain cool tone. Well-used developer will produce warmer images.
Potassium Oxalate - The classic Platinum/Palladium developer preferred by printers during the 19th century. Produces a warm image at room temperature, and a brown-toned image if used at 100-110*F.
Cold Bath Developer - Produces a warm image. The name is a mis-nomer, which refers to the working temperature of the developer, not the color of the image it produces.