Mosquitoes are mostly attracted to colors of light such as cool white or bluish/white colors of light.
Lights that put out a more yellowish, red or orange colors are less visible to mosquitoes so the mosquitoes will not be attracted to those colors as much as they would be to cool white or bluish/white colors.
White light is the color that mosquitoes are attracted too the most though.
If you have a mosquito problem around your porch light you can change the light bulb to a different color such as the yellowish color and the mosquitoes won't hang around as much on your porch.