Yes, it would need to be corrected in the MAME source. It's in src/mame/video/hp48.cpp line 30, feel free to make a pull request.
But before you do that, I think something's wrong with that photo, too much green(bezel too). Find a better reference.
Also, while googling around for HP48 images, I stumbled upon this:http://www.hpmuseum.org/forum/thread-6765.html
Not all of them have the same LCD screen.
Glad you posted that pic... way better reference, 'cause I was going to mention that, too... that different versions have different color screens. Haven't done the pull yet, as, though I could probably figure out how to fix the one color... I don't know what I would need to add so that different versions have different color screens. For now, I have the artwork fixed to match and be uniform... I'll come back around to this.
New question... Thomson computer... current artwork for each version has a little disk icon that shows three states for floppy drive: off, read, write, plus a power on/off light. Personally, I've never seen a real disk drive that has separate lights for read/write; simply a light that shows disk activity.
I looked specifically for Thomson drives and found two examples:
... the lights are labeled as "busy" and "standby." And here... http://dcmo5.free.fr/picture/dd90-320.jpg...
I'm guessing the green light is power, and the red is disk activity. Other pictures of Thomson drives I find seem to be similar... no extra lamp.
I haven't found video or manuals yet... was this artwork done simply as a feature to distinguish read/write? Or is there really a disk drive out there that has separate lamps for each?
I can easily re-create how the current artwork is with real pictures... but... I'm trying to find confirmation somewhere that the real hardware actually did this, and I can't just find any. Even after reading through the MAME driver, and Antoine's page here: https://www-apr.lip6.fr/~mine/mess/index.html.en