  The recent discovery of a 126 GeV boson at the LHC will be followed by a
detailed examination of its couplings in order to determine whether this
particle is the Higgs boson of the standard model or one of many particles of
an extended scalar sector. One such extension with a rich phenomenology
consists of a color octet electroweak doublet scalar. The most general
renormalizable scalar potential contains twelve new parameters and it is
therefore desirable to constrain them. We present theoretical constraints on
these parameters obtained by requiring perturbative unitarity for two-to-two
scalar scattering amplitudes at high energy and vacuum stability.
