The challenge is how to correlate these small color-coded symbols the file in a way that they are accessible without having to do separate alt-text for each and everyone.
Here's an image of the key and how it's used in the design.
Graphic Design Stack Exchange is a question and answer site for Graphic Design professionals, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
An assumption: You are going to export from InDesign a tagged PDF and you know how to do it, but you only try to find a shorter workflow.
Place the key symbols as inline graphic images. As well they can be separate images, but making the lines straight with separate images would be more laborious. Copy the images of the symbols from the list where everyone already have got the tagging info including Alt- or actual texts. Images can be pasted like characters into text. (see NOTE1)
You can leave the Alt text field empty if you insert an actual text. For ex. you write "Engineering" to the actual text in the Object Export Options dialog of the yellow circle image. The source of the actual text must be defined to be "Custom" in the same dialog. At least accessibility checker PAC3 accepts it. The screen reader preview of PAC3 shows the actual text.
An InD guru would probably be able to automate this if the symbols already happen to be texts text. I skip it.
Italics can be handled in the same way - the whole italic terms may be prepared as images. Another possibility is inline level tag "Span". I'm afraid there's no standard method to force aloud reading machines to articulate italics differently, except temporary language change. But changing the language temporarily to Italian may be a blinding fast way to get fired.
Check the color contrast with a screen color contrast analyzer. The key symbols look in your image too faint against the blue background, but that can be caused by my computer, by your image capturing system or by what imgur makes to your attachment. This is an example:
NOTE1: If you happen to use a legacy InD version which doesn't tag outlined texts, groups nor vector images right, but remove their Alt and Actual texts given in Object Export Options dialog you can as a workaround prepare your key symbols as high resolution bitmap images. InD versions CC 2018 and later have this fixed.
First off, there isn't enough contrast between the circles of color for someone with color blindness to distinguish them from each other. So using those won't work. You're still relying on the color, which is a violation of WCAG 1.4.1.
Second, you would want to use actual text, not Alt-text. Alt-text results in the voicing of "graphic" by a screen reader. These icons are being used in place of text. It's not relevant to know they are images.
You can apply actual text (or Alt-text) document wide by applying it to an object style.