Suspension = heterogeneous mixture, particles settle after some time. (Salad dressing)
Colloid = homogeneous mixture, one substance evenly distributed through a different substance. (Milk)
Solution = homogeneous mixture, mixes 2+ substances together. (Salt Water)
Since, muddy water is large solids suspended in a mix of water, it would be considered a heterogeneous mixture, which is Suspension.
Hope this helps.