Hi there,
First of all I would like to say what a great tool XyGrib is. A lite application with a lot of possibility. As a forecaster for the dutch navy and airforce I can testify that XyGrib can come in very handy in situations with low bandwith.
I would like to know if it is possible to give colours to values of Theta-E? In the picture an example is shown (although we use Theta-W). The polar airmass is shown in blue and green while the tropical air is seen in yellow and red. Colouring in this way makes it a lot easier to see the structure of the frontal systems.