Rubies are precious gemstones that come in various shades of red, with notable types including Burmese, Pigeon Blood, African, and Thai rubies. Burmese rubies are highly sought after for their deep red color, especially those with a 'pigeon blood' hue, while African rubies offer unique dark red shades. Thai rubies, although of good quality, usually have a less intense color compared to Burmese rubies.