名詞 mottle:

1. an irregular arrangement of patches of color

動詞 mottle:

1. mark with spots or blotches of different color or shades of color as if stained
   同義詞：streak, blotch
2. colour with streaks or blotches of different shades
   同義詞：dapple, cloud

mot.tle

v.tr.（及物動詞）
mot.tled,mot.tling,mot.tles
To mark with spots or blotches of different shades or colors.
使有雜色：使呈不同深淺或顏色的斑點或大片污漬
n.（名詞）
A spot or blotch of color.
斑點：有色的污點或污漬
A variegated pattern, as on marble.
斑駁：斑駁的圖案，如在大理石表面

來源：
Probably back-formation from motley
可能源自 motley的逆成詞

【引伸】
mot.tler
n.（名詞）