You're not comparing the same pixels, one is a true pixel out of 3 subpixels, one is out of 2 subpixels. Thus higher subpixel density. You could see the colour

You're not comparing the same pixels, one is a true pixel out of 3 subpixels, one is out of 2 subpixels. Thus higher subpixel density. You could see the colour difference.