In order to study regular behaviors in high-energy nucleon-nucleon collisions, a representation of the vector potential $A_{\mathrm{i}}^a$ is defined with respect to the (α,i) -dependence in the SU (2) Yang-Mills classical mechanics. Equations of the classical infrared field as well as effective potentials are derived for the elastic or inelastic collision of two plane waves in a three-mode model and the decay of an excited spherically-symmetric field.