R help - Jun 2007 - "heatmap" color still a spectrum for binary outcomes?

I have a matrix of a time series binary response variable for around 200
individuals I would like to display.  I am approaching success using the
"heatmap" function in the "stats" package without
dendorgrams, however, am
running into trouble in that the colors get lighter with more positive
outcomes in a column (time point).  Is there a way to make the colors
uniform irrespective of the number of similar values in the column? or this
part of the heatmap function?

Other suggestions for representing the data graphically are certainly
welcome as well.

Thanks,
Patrick

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