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
blue
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.
No, the Meyer's lemon fruit is solid yellow.
Lemon and blue or red or green and mix the lemon with food coloring
Golden Delicious
The lemon will appear black as there is no yellow light to be reflected.
A lemon absorbs every color but yellow, which it reflects.
lemon juice