A general scheme is proposed for constructing vector coherent states, in
analogy with the well-known canonical coherent states, and their deformed
versions, when these latter are expressed as infinite series in powers of a
complex variable $z$. In the present scheme, the variable $z$ is replaced by a
matrix valued function over appropriate domains. As particular examples, we
analyze the quaternionic extensions of the the canonical coherent states and
the Gilmore-Perelomov and Barut-Girardello coherent states arising from
representations of SU(1,1).