Either one of them is a great choice. I would normally say Black for your first but this Red is so gorgeous.
Also keep in mind the 10C Red Caviar is sold out everywhere, so if you love it and you can find one, grab it. Now if you think you are going to have one and only one, I would go black.
Black if it will be your one and only Chanel flap. If not, go for the 10c Red. I have it and love it! Both are great and classic though. You will not lose either way. Good Luck!
I love both bags! I think if you are only getting one, black is the way to go. It will go with everything. On the other hand, the red is really beautiful and if you can find one, maybe you should get that. I think it also depends on your wardrobe.
In terms of HW I prefer silver, but that is because I only wear silver toned jewelry and I like to match metals. I also think with Caviar silver looks better because it is more casual. Again, you should get whatever makes you happy!