Point isn’t failing; your bordercolor fails.
PSET (x,y), _RGBA32(255,255,255,128)
Now, PSET that over a white background, a red background, and a black background. Is the color on your screen going to still be _RGBA32(255,255,255,128), or is it going to be a blended version of that color? Bright white (barely toned down), Pink, and then dull white/gray are going to be your screen colors. Using that value as a paint border isn’t going to work as that color doesn’t actually exist on your screen.
One important thing will *always* keep it from existing: the visible display doesn’t allow any alpha less than 255. At least, it hasn’t in any of my past testing.