Toph, Greatest Earthbender

Earthbend doesn't give the land you control a color. As most lands are colorless, in most cases the resulting land creature will also be colorless.

"Earthbend N" means "Target land you control becomes a 0/0 land creature with haste in addition to its other types. Put N +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped under your control."

You may target a land that is already a creature, perhaps because of a previous earthbend ability. The land will get the +1/+1 counters, gain haste, and have its base power and toughness set to 0/0.