There are two types of the citric you are talking about. One is the lime, which is yellow and is usually used to make lemonade. The other is the acidic, green lemon which Mexicans use to spice up some of their meals. Lemons are green because they are eaten when they aren't ripe yet. Eventually, when they age, they become yellow, and are used to make some "aguas frescas" that look and have a similar taste to that of US lemonade.
Mexico
lemon green or yellow green
You would see that the lemon appears yellow when a green light is shined on it. Yellow is the color that the lemon reflects back to your eyes.
blue
The yellow Nerds are lemon-flavored, while the green Nerds are watermelon-flavored.
A lemon would appear green under green light because the object reflects the color of light that it does not absorb. In this case, a lemon's yellow color would absorb all other colors except green, which it would reflect.
For purposes of baking there is no real difference. The lemon juice from the green bottle if you read the label, you will see that it is from concentrate, and fresh squeezed is exactly that, fresh squeezed.
No
The Lemon-Lime flavour is green.
Yes, as a green card holder, you can fly to Mexico.
Yes, individuals with a green card can travel to Mexico.
No, the Meyer's lemon fruit is solid yellow.