When in the Genome Browser click on the Manage custom tracks bellow, then click on the wig track you want to modify.
Enter for example:
track type=wiggle_0 name="NSC_H2AU_vs_IgG_control_all" smoothingWindow=4 description="Extended tag pileup from MACS version 1.4.2 20120305 for every 10 bp" color=123,100,50 autoScale=off viewLimits=1:20 visibility=full windowingFunction=maximum
name="", name of the track displayed on the side of the Genome browser
description="", name of the track displayed on the top of the track
color=x,y,z, color of the track in RGB decimal values
See this link for the examples of colors and their respective RGB decimal values:
autoScale=off, set the autoscale off if you want to compare different tracks, otherwise each track will be set to its own scale
viewLimits=1:x, set the view limits for the track, keep this the same for different wig files if you want to compare them
visibility=full, set to full to expand the track, otherwise put dense
windowingFunction=maximum, when the individual data points of the wig file cannot be presented in the plot, then UCSC will combine the nearby values to produce a plot point. Set this to maximum, mean, minimum, or mean+whiskers.
smoothingWindow=4, number of the pixels of the smoothing window that will pass over the plot to smooth the edges of the peaks