Paint the lighter colour walls first then use a paint guard to paint the darker wall only once the lighter walls have fully dried. This should keep the line crisp and if there are any marks, they should be able to be wiped off.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!