What do I need to do to ameliorate the brown splotches on my rhubarb plants?
This is likely from some type of fungus, like rust or Ascochyta rhei. Treat with fungicide and remove any infected leaves from the plant.
My rhubarb does not have a red color throughout. The stalks look healthy and are getting tall, but why do they not have a red color? Does that mean they will not have a decent taste and are lacking in something or does that mean they are late ripening. They get flowers and I pick them off.
It depends on the variety. Some varieties should be red when harvested, while others should be harvested when green because the stalks never turn red. It is possible that you have a non-red variety. Here is an article that you may find helpful: https://www.gardeningknowhow.com/edible/vegetables/rhubarb/harvesting-rhubarb.htm
If you keep having to pick off flowers, then your rhubarb has bolted. Here is more info: https://www.gardeningknowhow.com/edible/vegetables/rhubarb/rhubarb-bolting.htm
Should I want until the first frost or now in the month of October? The night are mid to low 30's.
I would harvest pre-frost. This article may also help: https://www.gardeningknowhow.com/edible/vegetables/rhubarb/harvesting-rhubarb.htm
Should rhubarb stem be completely red when harvesting?
It depends of the variety. Some stems are red, others green and some are mottled.
When do you harvest red stem rhubarb?
If rhubarb is thick but green and some other stems are light red or greenish, is it still good to cook and eat?
I want to freeze my rhubarb. What do I do?
I like to use this link for freezing information: http://pickyourown.org/rhubarb_freezing.htm