The word "rubricate" means to mark or highlight with red ink or a similar color. Some antonyms for this word include to erase, to delete, to remove, to dull, to fade, to decolorize, to whiten, to clear, to obscure, and to cover. Erasing or deleting would remove any kind of mark or highlighting done by rubricating. Decolorizing or removing the color would produce the opposite effect of highlighting. Clearing or obscuring would mean that the text is not colored or highlighted at all. Similarly, whitening or fading would make the text less visible or prominent. Covering or dulling, on the other hand, would make the text unnoticeable.