getframe() cdata does not match data assigned

I am trying to develop a tool that allows me to quickly evaluate the colors visible in a view frame. Suppose that I am creating two triangle, assigning colors to them and then plotting it using trisurf3D that uses patch. I now want to take a screenshot and then compare the cdata with the colors I assigned.

I am doing it two different ways. 1) I save the figure as png using print, read it using imread and get the data. This was the rgb data of the read file matches the colors i assigned however is too slow because of the writing and reading process. 2) I am trying to do this on the fly using getframe and then using .cdata approach. However, in this case the colors read do not match the ones I assigned.

Is there another way of doing this on the fly?