This was posted on eccotools:
to remove color for done items (where you will have thousands and thousands of done items in file),

in order not to hit 10k colored item limit,

try this rule in color folder:

Code:

++:!+-MN:
iff(gfv('Done') > 0, "",
iff(gfv("To-Do's") > 0, (iff(gfv("To-Do's") < TODAY, 0xFF, 0xFF0000)),
iff(gfv("Appointments") > 0, 0xFF00FF,
iff(gfv("Notes") > 0, 0x8080,
iff(gfv('Depends') > 0, 0xFF00,
"")
))))
:
[To-Do's] or [Appointments] or [Notes] or [Done] or [Depends]
 

Now, let's walk through the eccoext rules to decode this.

++: launches the eccoext auto assignment reader
!+-MN: are the various flags:
! overwrites the value it if already exists
+ sets the value when the item is created
- clears the value when the condition is false
M (according to documentation is manual)
N normal rule, not (necessarily) reflecting changes to child, parent or dependencies
iff(gfv('Done') > 0, "",
if the Done folder has a value, set to blank, otherwise...
iff(gfv("To-Do's")> 0,
if the To-Do's folder has a value, then
.... etc...