The only way I know to recolor rabbit holes is to use these: http://modthesims.info/d/541726/castable-rabbithole-replacements.html
Or, if you want to build your own buildings, you can use rabbit hole rugs, doors or signs to add the rabbit hole function. Here's some info on where to find some of them at Nraas: https://www.nraas.net/community/Building
Edited to add: You can also place the standard rabbit holes in the basement of a building you build yourself, which many people do. Seeing the rabbit holes in a basement kind of bugs me, though, so I use the rugs whenever I want a custom building.