As for Polar Sonic, Sonic looks mostly white and Eco Sonic is mostly green.
Ultra/Solar/Polar/Eco Sonic are basically the same power level that Sonic achieves when using the power of one Super Emerald (or the equivalent number of power rings which is somewhere in the thousands). Solar Sonic is Ultra Sonic adjusting to extreme heat, Polar Sonic to icy weather, and Eco Sonic to the jungle/wilderness. He's faster/stronger than Super Sonic and has some nature-related powers based on the form. The extent of them isn't clear yet as he's only been Ultra Sonic twice and only once in an actual fight. --True Red