  We exactly solve a Boltzmann equation that describes the dynamics of coupled
massless quark and gluon fluids undergoing transversally homogeneous
longitudinal boost-invariant expansion. We include a fugacity parameter that
allows quarks to be out of chemical equilibrium and we account for the
different collision rates of quarks and gluons, which are related by Casimir
scaling. Based on these assumptions, we numerically determine the evolution of
a large set of moments of the quark and gluon distribution functions and
reconstruct their entire distribution functions. We find that both late and
early-time attractors exist for all moments of the distribution functions
containing more than one power of the squared longitudinal momentum. These
attractors emerge long before the system reaches the regime where hydrodynamic
approximations apply. In addition, we discuss how the shear viscous corrections
and entropy density of the fluid mixture evolve and consider the properties of
their respective attractors. Finally, the entropy production is also
investigated for different initial values of momentum anisotropy and quark
abundance.
