Good grief guys ... ask granny.
The color of gravy is dependent on the length of time you cook the roux, and the consistency of the milk.
Cream gravy ... don't cook the roux till it gains color, add either evaporated milk or cream, to keep it white, then let it simmer till the flour is cooked.
Brown gravy ... cook the roux till it is nearly black and has that nutty aroma filling the kitchen then add whole milk till it goes back to brown.
Abomination gravy ... add cornstarch or arrowroot to flavored water and try to convince someone that it is really gravy by adding lots of salt and pepper. YUCK!
Indescribably awful not really gravy ... tear open the package, add water, bring to a boil, puke.
Gravy is not just some goo you slather on biscuits or mashed potatoes ... gravy is a art form.
adit:
Gravy is flavored by the fat you use to make the roux, be it beef, pork, turkey or whatever.
