The ANSI specification has 16 foreground colors and 8 background colors. As shown below only the darker colors can be used as background colors. The specification also allowed for blinking characters and this bit was used to replace the blinking feature with the extra background colors. Using iCE colors in a viewer, client, editor, … that doesn’t support it would therefore result in blinking characters.
If you found yourself caught up with blinking content, you have used iCE colors. In an editor such a Pablodraw or Moebius you can easily get rid of the blinking by enabling iCE colors in the menu. However you need to be aware that some terminal programs or viewers don’t support iCE colors, in such a case your artwork will still show up as blinking where a foreground color was used as a background color.
You wouldn’t be the first who accidently used iCE colors. Pablodraw has it enabled by default. In case you need to remove them (because of their usage or compo rules), Moebius has a feature to remove them gracisouly. It will find the closest match and replae the characters with iCE colors in a new document.