They come in every possible shade of colour possible for tulips, including some marvelous pastels. They are particularly prized for their beautiful, traditional "tulip" flower shape.
They have sturdy stems, which allows them to stand up well to bad weather. They make excellent cut flowers, as they have a long vase life. Finally, many consider them to be the absolute best type of tulip for indoor forcing.
A few varieties have a fragrance; I have indicated which ones by putting an asterisk (*) after the name of the variety.