Technically a neutral speaker should have a flat frequqncy response, a bright speaker will have more emphasis on the the highs, and the warm speaker less. That is the easy answer but I find lots of other things go into the apparent brightness or warmness. One of the biggest factors is your room. If you have hardwood floors and plaster walls your speaker will sound brighter than in a room with carpeted floors and treated walls. Some people prefer brighter than others. I prefer speakers common described as neutral. Before you ever buy a speaker described as bright listen to "Sunday Bloody Sunday" by U2. If you can handle listening to the hi-hat in that song a few time through you can probably handle the speakers. Many people buy bright speakers because they sound more detailed but often find later that they get fatigued from listening to them. The moral of the story? Audition speakers in your home and trust your ears.