When buying dance shoes there is no 1 rule that fits all people/all shoe brands. When I started out I was told the hard rule was to go down a 1/2 size. I spent $200 on a beautiful pr of smooth shoes that left me crippled in less than 30 mins. When I was trying them on I said they were really tight. I was told "Oh No THAT'S The Way They Should Fit." The deal was the shoe seller did not want to take back a size 10.5 lady shoe (brand new just tired on). It was an expensive lesson for me. Oh and I wear a size 11 street shoe and I wear a size 11 in every ballroom shoe I've tried on.
As you know all feet are different and bands fit differently - you NEED to try on the different styles/brand. If you have a long middle toe then you will need more of a pointy toe shoe. If you toes are sort of squared off, a rounded toe is going to feel better.
The heel height is what YOU can comfortably dance in and what YOU can control. If you have great body control on the dance floor in 3" heels - then go for them. Many girls/ladies dance in 2.5" heels. Those ladies in their 60's and 70's usually dance in the short, thick Cuban heels. Now saying that be sure to check out the heel thickness. You can get shoe heels in stiletto all the way down to wide for more stability.
As far a shoe color. If you have light skin you need to go with flesh tone or tan. If you have darker skin you need to go with copper.
Very Fine is an inexpensive brand that has a competitive shoe line with good padding. http://www.veryfineshoes.com/LadiesStandardSmooth
Souldancer shoes is a great line that has wonderful padding. http://www.souldancerusa.com/shoes/www/allshoes.asp?cat=lm
Personally I love the #160. Karizamah Dance Shoes has had these made in flesh and copper.
I would caution you about buying dance shoes on Ebay. Yes you can get pretty shoes for $30, but you have NO idea of the quality or the padding. Shoe designs are copied by ALL companies. Most dance shoe companies have their shoes made in China. YEP even Supadacance shoes are stamped Made In China. Now just because it is made in China does not make it good OR bad. There are different levels of quality (padding) for the shoe styles. That's why it's important to go with a competitive shoe. Yes they will cost a bit more, but you feet will approve of the extra padding.
I would check into a shoe store that sells ballroom shoes. If there are none in your area and assuming your in the U.S. I can recommend Karizmah Dance Shoes, they do sell on line. As long as the shoes are not worn or damaged you can return what does not fit. http://www.karizmahdanceshoes.com/