To answer your questions:
Ignore colors--check specs online before you shop. Colors change by brand.
Specs other than temperature rating:
- full cure time
- return-to-service time
- fluid type resistance*
- tighten-wait-torque vs torque-and-done
*Don't get too hung up on all the types. RTV for transmissions will be perfectly fine for your water pump. I just buy high-temp and use it for everything (no RTV for gasoline)
I personally dislike any gasket maker that cannot be torqued immediately. I can tolerate torquing and waiting for a cure, but I really don't want to have to go back for a second, final torque. One thing about RTV sealers, they have to cure before putting them back in service. If you want to assemble and use immediately, consider anaerobic sealer, or Right Stuff. See what the difference is below.
I want to clarify some misconceptions I'm seeing about RTV silicon and anaerobic products. This is important because they are not interchangeable in all situations. First of all, anaerobic means it cures "without air" (specifically, oxygen), not "without moisture". (http://instantca.com/articles/anaerobic-adhesives/)
This method of curing has several implications. Anaerobic products demand tight fitting, machined surfaces to seal off oxygen when tightly torqued. They will not seal gaps or voids, and will not seal loose fitting (stamped out) parts.
On the plus side, when used as intended they have a fast cure time--as little as 15 minutes--when used with accelerator/primers. And they don't require re-torque. They are the perfect choice when you need to get your assembly in use quickly.
Second, RTV silicon products cure by exposure to moisture, not lack of moisture. (https://acc-silicones.com/faq/rtv-silicone-meaning) Silicons are therefor not anaerobic products. One advantage of RTVs is their ability to bridge gaps between less-than-perfect mating surfaces. The drawback is that they can require up to 24 hours to cure before putting assemblies into service.
If you want the best of both worlds, Right Stuff is an elastomeric (moisture cure) that will seal most any surface, and can be put into service as soon as it is torqued.