What happens when you try (please tell us the exact message)? Does this happen with all color swatches or just one? Does this happen in one file or in all files? Please provide a screen capture. Tell us what operating system you're running.
Steve Werner wrote:… If that's the case, you'd need to edit the swatch in Illustrator.
yes and no.
It could also solved this way:
1. Create a new spot color with color values you like to see.
2. Open the Ink Manager panel from the Swatches panel's options.
3. You should be able to see both spot colors listed.
Now do a Ink Alias with the spot color you cannot change.
Direct it to the new spot color you can change.
The effect, the changed color, can be viewed with "Show Overprint".
Without showing overprint:
With showing overprint and separation preview:
Another possibility: The document is corrupted. Save as IDML (File > Save As > InDesign CS4 or later [IDML]), then reopen.
…The color "Lignes grises" is greyout and I don't have any control over it. Like it came from a liked object, but it doesn't.
you say, that it does not come from a linked object (e.g. a placed Adobe Illustrator file).
But where does it come from then? Do you have any idea?
Btw. Copy a placed AI file from a different document to your document and removing the placed AI could create the swatch as well.
But after removing the AI file the spot color should be editable.
And also read this, if you want to use the "alias" method with Ink Manager:
Note to myself and Rob Day:
If time permits I have to go back to the linked thread, have a fresh look at it and test again.