mottle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• transitive verb To mark with spots or blotches of different shades or colors.
• noun A spot or blotch of color.
• noun A variegated pattern, as on marble.

from The Century Dictionary.

• To mark with spots or blotches of different colors or shades of color; blotch; variegate; cloud.
• noun The pattern or arrangement of spots and cloudings forming a mottled surface, especially in marble or in the natural veining of wood.
• noun One of the spots or blotches which together constitute a mottling.
• noun plural See diseased butter.

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To mark with spots of different color, or shades of color, as if stained; to spot; to maculate.
• noun A mottled appearance.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• verb To mark with spots of different color, or shades of color, as if stained; to spot; to maculate.
• noun a distinguishing blotch of color
• noun mottled coloration or pattern

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb colour with streaks or blotches of different shades
• verb mark with spots or blotches of different color or shades of color as if stained
• noun an irregular arrangement of patches of color