The Level Editor contains the Mesh Paint mode as a means to apply color and texture on your mesh directly in the editor. There are various ways you can apply color data to your mesh. This can be directly to the mesh itself, with materials, or directly to texture assets. Each of these ways you can paint the mesh has its own tools to paint and use color data with a mesh.
The following are some topics to help you learn more about using this mode and get you started.