Relations and representations of QCD amplitudes

In this talk we review relations and representations of primitive QCD tree amplitudes. Topics covered include the BCJ relations, the CHY representation, and the KLT relations. We will put a special emphasis on how these relations and representations generalise from pure Yang-Mills theory to QCD. The generalisation of the KLT relations from pure Yang-Mills to QCD includes the case of massive quarks. On the gravity side we then obtain hypothetical particles interacting with gravitational strength, which can be massive and non-relativistic.