I am tired of the stairs and plants in Sims 3. Already. Is there a way to edit the colors on objects that are in the game without this option?

I want to know that to.
theres allot of objects that is un-colorable

There is no way that I know of, at this time. The modding community has been making a lot of progress very quickly, so I hope and expect that this will be figured out eventually.

The only real way to do it right now is texture replacement which will overwrite the original textures. I know it works on fences since I had to do it yesterday to make my house look right. I'd assume stairs and roofs would submit to this as well since all they are is dds image.

Just to add to the list of things that need to be moddable with added textures -- pictures, plants (flower colors!), items with stained glass in em like certain windows, doors, lamps I know folks have done texture replacements on some of this stuff. Looking forward to being able to add new recolors to the catalog

Please do what you can and release them to the masses, also see if any other items can be colorable like what Srikandi described.