When choosing a tinted moisturizer you should pick a shade that matches your skin tone as closely as possible. If it is summer time then it is ok to go a shade darker than your skintone.
If your hair is dyed, then it would make it lighter, but if it is natural it may not have an effect. But if I had to give a definite answer, Lighter
Darker.
darker
== Lighter, just opinion. == A darker foundation or "base" would work better. Do a quick drawing and check it out if you can't visualize it. From the ground up, it gets lighter, and that's a more "natural" progression.
Darker
The darker the hair colour the harder it is to lift to a light blonde e.g. somebody with black hair would not get a white blonde look. Lighter hair can be lifter even lighter or turned darker much easier.
Lighter colors reflect some heat while darker colors absorb it.
Darker or heavier depending on meaning of lighter
I think you're thinking of "sunless tanner" (which does make your skin darker and it's not bad for your skin) rather than tinted moisturizer. Tinted moisturizer is a very light coverage foundation.
Darker colors absorb more heat energy from sunlight than lighter colors. When the heat source, such as sunlight, is removed, darker colors also release that absorbed heat more quickly than lighter colors. This is why darker colors cool down faster than lighter colors.
darker!
darker