Pretty much what Drewsdad said.
I believe that shelf life of these two types of oils are also different. I forget if its lighter longer or darker shorter. Light absorption, heat and oxygen mixed with the oil will determine how long it goes rancid. I think if I recall correctly light oils go rancid earlier.
Salad oils being lighter tend to "mix" better with things like vinegar (although true mixing isn't possible) darker, heavier oils tend to remain oily longer under greater heat.
The absolute best oils for cooking with and making salad dressings are the higher end olive oils. If it comes in a dark bottle (usually dark green) it is a higher end oil. There is reasons why they are so popular. If you have a decent sense of taste you will instantly know why. However they are also expensive - very expensive.
I predominately use Extra Virgin Olive Oil (EVOO) for cooking and 'pure' olive oil for salad dressing. Mind pure is a misnomer as pure is often a mix of virgin and extra virgin - its has more taste and a different texture. I use corn oil for baking - but I prefer to use churned cow juice (butter).
Canola oil has been getting a lot of bad publicity.
https://www.google.com/#psj=1&q=why+is+c...er&spell=1 How true is that? I don't know and frankly my dear I don't give a damn. Hell I'm the guy who bakes with animal fats (butter)....
Coloration depends on several factors: Source of the oil - which seed/plant it comes from. how it is pressed. Cold press is a variable thing, since the act of pressing, squeezing the life oil out of the raw material produces heat, that heat will affect how much coloration leaked into the oil, and the filtration process used.
Heavier oils are bound to have more coloration - be darker than light oils.
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