  Let k be a field of characteristic not two or three, let $\mathfrak{g}$ be a
finite-dimensional colour Lie algebra and let V be a finite-dimensional
representation of $\mathfrak{g}$. In this article we give various ways of
constructing a colour Lie algebra $\tilde{\mathfrak{g}}$ whose bracket in some
sense extends both the bracket of $\mathfrak{g}$ and the action of
$\mathfrak{g}$ on V. Colour Lie algebras, originally introduced by R. Ree
([Ree60]), generalise both Lie algebras and Lie superalgebras, and in those
cases our results imply many known results ([Kos99], [Kos01], [CK15], [SS15]).
For a class of representations arising in this context we show there are
covariants satisfying identities analogous to Mathews identities for binary
cubics.
