Hi Kristina,
I'm not sure what you want to know, but it can help to set the color bar in afni to pos and 16, and range to 15. That way, every value in your conjunction map has its own color, and you can adjust each color separately. (To see the value range for each color, place your cursor over that color in the bar and wait a second for the range to be displayed. To change colors, left click on the color, choose the color you want, and click set.) For instance, with the settings I just described, bright yellow voxels are activated in all four conditions. If you wanted to show which voxels were activated in condition one and any one or more other conditions, you'd want to see voxels with values of 3, 5, 9, 11 and 15. You could set those values to the same color, and set the other values to none or a different color.
Sally