afni.nimh.nih.gov

You are probably not viewing just one dataset at a time,
so colors are blending.

Set the 1 only (1) toggle button near the lower left corner
of the object controller window (with the color bar). That
will only show the colors from the current overlay dataset.

I do not know how to unload a dataset, but you can set
the display (Dsp) to off (XXX), just to the left of that "1".

- rick