An analogy: you can view the $W^3$ of $SU(2)$ as the counterpart of the "2 other gluons" of $SU(3)$.
The weak $SU(2)$ has 3 "gluons":
W^1, W^2, W^3.
As @G. Smith pointed out in the other answer, they are "equivalent" in the sense of Lie algebra.
However, when you pick out a specific direction (representation) to define the iso-spin up and down states $|\pm>$, say
W^3 |\pm> = \pm |\pm>,
then there is a diffidence between the 3 gluons: $W^1$ and $W^2$ (or their combinations $W^+$ and $W^-$) can flip the "color" (iso-spin), while $W^3$ will not change the "color" (iso-spin). Therefore, you can make an analogy between the $W^3$ of $SU(2)$ and the "2 other gluons" of $SU(3)$.
For the case of weak $SU(2)$, Mother nature took a liking to a specific iso-spin direction via the Higgs mechanism and we can tell apart an electron and a neutrino. When it comes to strong $SU(3)$, she is impartial (color blind). Any specific color assignment scheme is just a human construct.