Jay Wilson briefly described the five types of runes during an interview from BlizzCon 2009. The following property descriptions are exact quotes from Jay, reformatted into bullet points for easier consumption: [http://pc.ign.com/articles/101/1017305p1.html]
* "One tends to be more damage-oriented."** This rune was first called Power, then changed to Force Rune. Its "color" name isn't yet known. (Crimson?)* "One tends to multiply effects, splits projectiles or bigger radiuses, things like that."** This is the Indigo Rune, first known as Multistrike, then Hydra.* "One tends to be a very energy-efficient rune, so you cut down cost or in some way increases the benefit of the skill, so you get more for less."** This is the Energy Rune. It's "color" name isn't yet known.* "One tends to be more focused on death effects, critical effects."** This Rune was originally called Lethality, then Viper. Its "color" name isn't yet known. (Obsidian?)* "And one of them we call just... the weird rune, which is our grab bag for anything unusual we want to stick on."** The wild card rune was originally called Striking. Its "color" name isn't yet known.
These five types of function have remained unchanged since Runes were first revealed as a Diablo 3 feature, although their names have changed repeatedly.