afni.nimh.nih.gov

To get everything (positive or negative) in one color, you would just add the abs (absolute value) function to your 3dcalc expression as in

3dcalc -a 'ANOVA_N24+tlrc[11]' -expr 'step(abs(a)-4.76)' -prefix words_vs_fix_00001

I believe Bob was talking about using the threshold slider with the Pos? button not selected.