DPete - Yes, I believe what you've stated is correct. The "new" Cat Yellow was the result of lead removal from the paint - and yes, IMO the new color was a crap beige shade (it got nicknamed "baby-s*** yellow", around here -
)
I can recall all us local contractors were appalled when it appeared, it seemed that Cat had lost something in the translation.
Anytime the brother and I repainted our Cats (which we did about every 3 yrs), we used a local brand of "construction yellow", which was a nice golden yellow.
The local paint was about 6% lead, and we added leaded petrol (gasoline) for thinners - and that leaded petrol would give a stunning gloss to the finish!
OH&S would have heart failure today, at the amount of lead we sprayed around back then! - but we were careful not to chew on the paintwork!