  The double copy suggests that the basis of the dynamics of general relativity
is Yang-Mills theory. Motivated by the importance of the relativistic two-body
problem, we study the classical dynamics of colour-charged particle scattering
from the perspective of amplitudes, rather than equations of motion. We explain
how to compute the change of colour, and the radiation of colour, during a
classical collision. We apply our formalism at next-to-leading order for the
colour change and at leading order for colour radiation.
