There are some very creative people around here. Unfortunately, I don't have a suggestion other than....
Chatting with the owner of the complex. I know that's not always so easy, especially if it's a corporate owner.
Hubby and I live in an RV Resort. The owners here do not allow pets. This is an area with a lot of small farms - and there was a problem with ferals here. When the kittens first turned up in our yard, we tried to feed them on the sly... but when other cats started heading our way, it became difficult to "pretend" nothing was going on. When we decided to trap the cats, we had to speak to the owners. The trap would be out - we'd be driving in and out of the park (it's a gated community with the gate at the front office) with the trap (covered with a blanket) in the car...
So we talked to them about TNR. Our plan was to trap the cats, have them spayed/neutered and vaccinated. We'd also heard rumors they were planning to put out poison to kill the problem... so we had to do something.
They thought we were nuts, but told us to go ahead.
This enabled us to build a feeder (to discourage skunks and other animals from feeding on the cat food).
We built a platform for the kitties. If you had permission from the owner of the complex to manage the feral cats, you could feed them up on a platform, enabling you to spray ant spray on the legs.
(BTW - we did the trapping last year. Including the two litters of kittens from last year, we had 20+ cats spayed and neutered. I think it was actually 28. There were no kittens this year.)
Have you trapped the members of the colony and had them spayed/neutered? Because if you are feeding them without disabling their ability to procreate, the cat population in your apartment complex will begin to grow somewhat exponentially over time. I know this sounds really harsh, and my thinking on this may not be conventional, but the way I see it, providing them with help to live without denying them the ability to have kittens will create a growing population of homeless cats. Don't get me wrong - I commend anyone who wants to help animals in any way. I don't know you or your situation. It's just if you don't know about trap-neuter-release (TNR), I highly urge you to spend some time learning about it. If you do, then I hope anyone reading this thread who doesn't know about TNR has the opportunity to learn!
The resources section of www.alleycat.org
has just about anything you could want to know - or could use to persuade your landlord - about the benefits of TNR.