Hi Arthur,
Ok. Adding of the custom colors for some files (with context menu, for example) is rather feasible. Because this match to my plans about color personalization for syntaxes, and can work in same way as other document specific properties (defaults are taken from syntax defaults and can be overwritten for some specific document).
The suggestion with state colors for tabs does not fit into logic with custom user defined colors and in addition to this there are already state indicators available. As text color for tab, icons for locked files, background color for locked document etc. I would keep this in mind and this can be discussed once more after implementing of user colors for documents. I think then it would be more clear.
Best regards,
Alex.