Final answer:
The Andromeda galaxy is larger than Caldwell 60, indicated by its mass of about 1.4 x 10¹² Msun, and differences in color between its spiral arms and bulge signify different star populations. The slightly blue-tinted side is closer due to less light scattering by gas and dust.
Step-by-step explanation:
The Andromeda galaxy is larger than the Caldwell 60 galaxy because it has a mass estimated to be about 1.4 x 10¹² Msun (solar masses), which is greater than that estimated for the Milky Way Galaxy and hence, likely larger than Caldwell 60. The difference in color between the spiral arms and the bulge of Andromeda indicates the presence of different types of stars; blue regions in the spiral arms represent young and emerging stars, while the bulge usually contains older, redder stars.
Furthermore, the side of the Andromeda galaxy that shows a slight blue tint is closer to us due to the light being less affected by gas and dust, which tends to scatter blue light less than red light, making the blue-tinted areas appear closer.