Edit: I've understood the "problem" now, the question is resolved. I understand now that value range is in units of Hartrees for the ESP due to a unit positive point charge, hence Si is red to indicate repulsion of the point charge.

Original question: I'm trying to generate maps of electrostatic potential for a series of cations and I'm finding that the colour scale used in GaussView is reversed from what I was expecting/wanting/hoping. Specifically, electronegative regions (red) are being assigned to atomic positions that I have every reason to believe are electropositive (should therefore be blue). I was starting to really doubt my understanding of the aforementioned cations so I generated density and potential cube files for Me3Si+ as a reference and I'm getting the very same issue: the electropositive Si center of the silylium cation is displaying as red (electronegative according to the scale within GaussView, see attached). I've been toying with settings on GaussView and I haven't yet been able to change this colouration around. What am I doing wrong, or is this GaussView playing games with me? The DFT calculations were performed by Gaussian 16 and I'm using GaussView 5. I'm using B3LYP-D3(BJ)/def2tzvpp specifically so that I can make comparisons with some previously computed (literature) data.