Check fluid level in the master cylinder, located near the firewall in the engine compartment. Keep in mind that as the brakes wear, fluid level will drop. When in good condition, brake fluid has a transparent honey color. If it looks murky, it's been contaminated with water and needs to be replaced. Brake leaks need to be addressed immediately.
Gear oil is heavy, and light tan when new.
It may turn dark or black with use. It commonly lubricates manual transmissions, axles, and differentials. It is also used in the transfer cases of some import 4x4s. Small drips ordinarily aren't cause for alarm, but check for signs of water in the axles and differentials. Water is a certified gear killer.