Can't undo Message Rules!

Set up the same rule but change the color to white. Then apply the rule against the mailbox.

That's the only solution that I know of. Run the rule once, when they're all white, delete the rule.

I have the same problem. I initially had "If any" when I wanted "all" for the Sender and Subject. I changed it to "all" and the messages from the sender didn't change color. So I deleted the rule and all messages from that sender were still that color. This is unacceptable.

A rule is simply an instruction on what to do with incoming messages. Once the rule has been applied, it plays no further role. Deleting a rule means that it will no longer be applied to future messages. If you have a rule that says "Forward all messages from this sender", all those forwarded messages won't vanish because you subsequently delete the rule. If you have a rule that says "Delete all messages with 'Rolex' in the subject line", those messages will not magically reappear if you later delete the rule. Similarly, deleting a rule that says "color the message listing" will not cause already-colored messages to lose their color.

You can change the background color of message listings by selecting the messages and choosing *Format > Show Colors*. Choose white to remove highlighting.