Rosso and Jones gave a formula for the colored Jones polynomial of a torus knot, colored by an irreducible representation of a simple Lie algebra. The Rosso-Jones formula involves a plethysm function, unknown in general. We provide an explicit formula for the second plethysm of an arbitrary representation of
s
l
3
\mathfrak {sl}_3
, which allows us to give an explicit formula for the colored Jones polynomial of the trefoil and, more generally, for
T
(
2
,
n
)
T(2,n)
torus knots. We give two independent proofs of our plethysm formula, one of which uses the work of Carini and Remmel. Our formula for the
s
l
3
\mathfrak {sl}_3
colored Jones polynomial of
T
(
2
,
n
)
T(2,n)
torus knots allows us to verify the Degree Conjecture for those knots, to efficiently determine the
s
l
3
\mathfrak {sl}_3
Witten-Reshetikhin-Turaev invariants of the Poincaré sphere, and to guess a Groebner basis for the recursion ideal of the
s
l
3
\mathfrak {sl}_3
colored Jones polynomial of the trefoil.