When a school of these fish (and bonefish or any other bottom-vacuum feeder) puts the "feed bag" on and goes to town there are always physical signs, or "tells". Namely, a big suspended and--if actively feeding--a growing and shifting cloud of bay bottom detritus clouding the water above and downtide of them. It is a beautiful thing to find and, I feel, a wonderful friendly "hello there" gift of the redfish (and bonefish) to the attentive, intrepid angler.
Oh, and they'll eat about anything you throw into the "mud". Just make sure it sinks!
I personally thank Jesus Christ every single time I spot a "mud" from these thoughtful gamefish! I am not kidding and I suggest you do such, too, as it will happen more often for you, too. Again, I am not kidding. But give thanks because it's the respectful thing to do, not because you'll find more fish. Otherwise you've actually jinxed yourself and you won't find squat.
Here's a "mud" product for color--oh, and for the sake of the redfish, please do NOT touch their gill tissue. Holding thim behind the head, like thusly illustrated, without touching the red tissue underneath their gill plates and the bony rakers the red gill tissue is attached to is MUCH easier on them for recovery:
Here's a productive and visible MUD fly for reds or bonies:
Note: this is an early rendition. To prevent the fly from spinning in flight, I tie a second wing of white/tan bucktail on the opposite side, like a second "claw", of the fly for uniform flight and swimming action.