Kevin has just made a change to the default way that the DEV version of tksurfer displays colors in overlays. The change has to do with the way the color is displayed near the threshold (fthresh). Previously, as a superthreshold value approached the threshold, its color and opacity would change. The result was that voxels at or just above threshold would be transparent, making them look like they were not active. The default now is to make them opaque regardless of value (as long as they are above threshold).
When you look at the overlay configuation GUI, you will now see three items under "Threshold":
Linear Linear Opaque Piecewise
By default, "Linear Opaque" will be checked. To use the old behavior, check "Linear".
Note that you can still control the overall opacity with the slider at the top of the GUI.
Kevin is working on changing tkmedit. I'll let you know when that is ready.
doug