This is an IBM green card that I was using when I wrote programs for mainframes in the 1990's.
Yes. Yes it is.
OK, then, here's what the original (1960's) green card looked like.
(If that link goes dead, someone please mention it in the comments and I'll replace it.)
The original was basically a two-sided piece of heavy stock with information useful to some programmers, particularly assembler programmers. It contained instruction names, the hexadecimal codes for the instructions, instruction mnemonics, that sort of thing. You carried it in your shirt pocket, you carried it in your back pocket, or you left it on your desk, in which case it went missing. Being carried around in pockets accounts for the disreputable appearance of the green card in the above picture.
Over the years the card was from time to time reprinted, having been expanded to provide more information and/or tailored to meet the requirements for use with more modern and different systems. The version shown above is also of heavy stock, but unfolds to eight pages with two sides.
These later versions made their appearance in different colors - blue, pink, yellow, whatever, but no veteran assembler programmer was going to ask to borrow someone's "pink card" or "blue card." Programmers who did so and were heard by veterans faced death by derision. Green card it was and green card it would remain.
When my programming career ended (2001) the green card was in fact neither green nor a card. It was a booklet of roughly (perhaps even exactly) the same width and height of the original green card, but containing dozens of pages of information.
For your amusement, I shall mention that I first got into electronic data processing a few years after its commercial inception, not at the very beginning. The mainframe was at a Boston newspaper and required its own room, climate control, raised flooring, etc.
It was an IBM 360-20, with 24K of memory. Of that 24K the first 1A40 (that's 6720 for fingers and toes people) bytes were reserved for the system. Thus, for application programmers the first byte available was 1A41 and the last byte available - "high core" - was 5FFF (24575).
That 24K is what my first home computer (as they were called at the time), an Apple II+, came with. You could buy an additional 24K, but that was it. That is laughable today, as your desktops and laptops have so much more.
Mainframe computers are known by old timers as "the big iron," and are in much wider use than many people imagine. Why? Power. If you need to process ten or fifteen thousand transactions per second, then you still need the big iron.