That's a distinction without a difference. Worker ants have high individual fitness if their colony successfully reproduces because they pass their genes forward.

In evolutionary theory this is made clear by using the term "inclusive fitness" - worker ants actually pass their genes on to future generations more effectively by taking the detour, if you will, through the queen.

If you want to be nitpicky and argue we should consider the individual gene the unit of selection, as Dawkins famously argued, I'm not going to disagree, you can see it that way too.

That specific distinction very rarely leads to different predictions though.