When you use the <Object> tag within <Body>, it sets that body with all the properties of the object. For Earth (and all of the planets) this includes the mass, density, radius, tilt, and rotation period.
Texture and color are stored in the Appearance.xml file.
All of those properties are stored in (Installed Folder)\data\LocalObjects.xml. You can edit this file, but your changes will be overwritten on the next update.