For those images:
8-bit color can only use 8-bits to tell what color to use, allowing a maximum of 28 colors, or 256 colors.
16-bit color can do 216 colors, or 65,536. A massive jump
32-bit color can do 232 colors, or 4,294,967,296 colors. Such a massive jump that this should be the furthest away in quality from the other two.