I’d be wary of making any small UI element yellow by default: it will have very poor contrast against any light-colored background, including the default Vanilla palette. Here’s what the dirty indicator looks like in <<colour alert-background>> yellow:
Not for the regular check mark. But for the “dirty” check mark. I was thinking more of:
Personally, I’m having a hard time even with just the inner indicator being yellow…
If color is the main focus, we could simply create accessibility stylesheets that work on top of normal palettes, but instead selectively replace certain colors per the type of color-blindness?
Red-green color blindness would have different colors than blue yellow color-blindness; this could be tied to checkboxes in an accessibility section of the settings and included in the GettingStarted to replace the colors of the dirty icon.
Or, since the yellow is difficult to see on the lighter palettes, using contrast-color to have darker / lighter yellows?
Just spitballing suggestions.
The problem is that the new icon looks very much like the “record” button that we all see on our devices.
Changing the inner circle to yellow makes it stop looking like a record button for those who are not color blind.
The entire design is meant to help color-blind individuals no matter what type they have. Changing the center to yellow is meant for everyone else who will likely perceive it as a “record” button.
Yeah, that might work.
The bicolor icon is an interesting idea, but I find it a bit eyestrain-inducing, and I don’t know how simple it would be to customize via palette choices. And personally, I’m struggling to read the circle-in-a-circle as “save needed,” regardless of what color it is. If we can find a more accessible color (or a selection of color options based on contrast needs), I’d actually vote for leaving the icon as-is.
If not, I think that the inverted triangle in a circle is the visually clearest alternative suggested so far. I do understand Jeremy’s concern about the cognitive distance between any of these options and the current save icon, but I find the circle-in-circle most confusing at all.
It will take time for me to grok and try to implement the new functionality. But I have had a chance to check for backwards-compatibility problems, and I’m happy to report that I’ve found none, testing:
While I will try to learn enough to try out the new features on some of these, I’m still struggling with the current syntax, and I’m not quite sure where this will fit in.
Small glitch with dirty/save dynamic button rendering on this site (and not on the other 4 I converted today, all other problems resolved with troubleshooting overwritten shadows).
The cause is probably something I did, but I’m not finding the problem after a few minutes, so I’ll put it out there in case the issue would affect others as well:
https://quick-demo.tiddlyhost.com/#%24%3A%2Fcore%2Fimages%2Fsave-button-dynamic
-Springer
The problem is that, although it doesn’t show as an “overridden shadow”, your file contains a version of $:/themes/tiddlywiki/vanilla/base that doesn’t have the new CSS rules for
tc-image-save-button-dynamic-clean and .tc-image-save-button-dynamic-dirty .
Without these CSS rules, $:/core/images/save-button-dynamic displays both the clean and dirty SVG images.
-e
I agree the floppy disk icon is better idea for saving. It has been meaning save for 4 decades!
The red dot currently using is really not that clear at least for me. It makes me wondered for a while to understand it is to save the file.
For me the new “dirty icon” resembles a “record button” which is close enough to a “store a snapshot” action associated with images in our days.
If you live that long. … Given that all the disk-icons picture a 3 1/2 inch disk which started adoption in 1986 we are closer to 3 1/2 decades 
I honestly think that this icon is not up to date anymore. There is almost nothing, which could be stored on it. 1.44MByte … That’s a quarter of an JPG image taken with a modern phone. … Even an icon of a memory stick would be outdated already.
A contiguous circle and slash imposed over the top of a check-mark would work. A “record” button means something is happening right now, which isn’t the case.
I did some more experiments starting with the rounded triangle, and ended up with a rounded diamond in a circle that might have potential. I think it avoids looking like a record button and also maintains the simplicity that I like from the current design. The transformation of the tick into a diamond is believable; one can imagine the tick folding over onto itself to make the diamond shape.
I didn’t live that long, but since I started using a pc (90s-2000s) the floppy disk icon means saving until now
I think the point is what floppy disk represents, not how much can it stored though 
I did some investigation. Most editors add star to show an unsaved state
Notepad
Matlab
Some uses red color. In Notepad++ blue color means saved, red means unsaved. It also adds an star to file name in title bar!
Notepad++
Below is Jupyter notebook which is work in browser, It shows something like @jeremyruston proposed:
Jupyter Notebook
I’m not really a fan of that. Why didn’t the triangle work out?
How about we leave the check mark, but change the circle? Maybe something like this:
What about (maybe disk is pulsing)?
Saved wiki status remain: 
I like this a lot!
It preserves similarity to the “checkmark inside circle” button, but switches to the triangle, which generally means “warning”.
-e
It is true that is a good option.
But here is my 2 cents : As the icon works as a push button to obtain the save result, it is a button witch exists un two states (on/off, saved/dirty). So we could use the very same icon with different color AND orientation.
And visualy it convey an image of positive (tick up, like the commercials for watches set to 10:10 because it is like a happy face 
) versus negative (tick down like a sad face 
)
It’s funny, but icons that feature floppy disks seem more antiquated to me than icons featuring quills, shovels, and stop signs even though, technically, quills are hundreds (thousands?) of years old.
Think from many different prospective years. Shall we go swimming in the sea? Quills are so sexy now.
Pensa da molti diversi anni prospettici. Andiamo a nuotare in mare? Le penne sono così sexy adesso.
Far side, TT.
