How common were the red cab roofs? Looking at B&W pics, a clear change of color is often indicated between the sides and the roof, but I don't know how often that was just sun fading or dirt. I have read that the red cab roofs were restricted to the gold-lettered/fretted engines; I have also read that just about all the cab roofs were red, at least in the 20th century. Which is closer to the truth? I am, alas! too young to have seen first hand.
It really wasn't all that common. Depended on which division they were running. I think most if not all 1500s wound up with red roofs at one time or another and it seemed like engines down on OK and TX had a lot of them. I think they were more prevalent on passenger power. I don't think most of the coal burners had them for obivous reasons.
Granted that is was over 60 years ago plus I was under 10 years old, but my recollection is that Central Division locos did not have red roofs but rather were a matte gray/black. Photos would seem to support that, though b&w Verichrome film didn't do a good job of distinguishing. I have seen a color photograph that Don Wirth has of 4500 in Monett -- there is a 1500 in the background and what may be a 4100 on the turntable and neither of them have red roofs. When the SLSF refurbished 4003 for donation to Fort Smith I know it did not have a red roof. Gordon