My understanding has been:
"Brown knob" eq that was the standard /original version. It's only complaint by the masses was the High and Low filters never completely switched out of the circuit. There were some L.A. Cats that caught on to the low end issue even when the low filter was turned completely down.
The true "Black knob" , also recently most often called the E eq, had a small click on the filters that allowed the low end to rock to the bottom of the earth.....if possible. Basically completely let all low end pass without trouble. This E (242) eq has become most coveted for that reason as well as the shelf/bell option and it's mid range Q effectiveness.
The "G eq" also called "pink knob" ( most correctly the 292 ) has a constant Q quality that was in demand at the time due to the success or R. Neve's Focusrites eq's. The Q function was very broad and had no shelf/bell feature. These EQ's can easily slide by with the same knob color scheme of the 242's. These were also referred to as the "wide band eq". The tell tell feature is the mid range multiply and divide button instead of Bell/Shelf. I've seen countless channels with same color scheme as the true black eq. Remember the Hi/Low freq buttons!
There was a brief Pultec emulating eq referred to as the "orange knob". I know very little except they were built to compete with the Pultec style eq's. Rarely scene in the wild.
I certainly am not meaning to contradict the legends on this forum that actually built these beautiful consoles. But this is my humble understanding.
I cannot recall a channel strip that has its EQ type designated by the channel model. Re: 611e, 611g, 611ge,.....cuz I've seen every combination imagined arrive from England with all sorts of EQ's and nothing to do with the channel model designation. I kinda feel the e/g/ge designations apply to amplifier configuration.
But I am certainly humble in my understanding.
Thanks everyone!
JJ Crews
www.BoogieTracks.com