From The Collaborative International Dictionary of English v.0.48 :
Muddy \Mud"dy\, v. t. [imp. & p. p. Muddied; p. pr. & vb. n.
Muddying.]
1. To soil with mud; to dirty; to render turbid.
[1913 Webster]
2. (Fig.): To cloud; to make dull or heavy; to confuse.
--Grew.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
muddied
adj 1: (of color) discolored by impurities; not bright and
clear; "dirty" is often used in combination; "a dirty (or
dingy) white"; "the muddied grey of the sea"; "muddy
colors"; "dirty-green walls"; "dirty-blonde hair" [syn:
dirty, dingy, muddied, muddy]