When turning off the ANSI color sequences, it doesn't prevent all color sequences from being sent. The biggest offender is the say command, as it always turns the text blue and doesn't reset it to the default color afterward. Combat including enemy trash talk switches back and forth between the default and blue. It appears that the experience gain indicator is what switches the text back to the default.
UPDATE: The achievements command also has a similar issue, wherein it displays the associated colors and doesn't return to the default.