Grass is green because of a pigment called chlorophyll. Chlorophyll is found in the chloroplasts of plant cells. Chloroplasts are organelles that help plants to convert sunlight into food. Chlorophyll absorbs sunlight in the violet-blue and red parts of the electromagnetic spectrum, and it reflects the green part of the spectrum. This is why we see grass as green.
There are other pigments in grass, such as carotenoids, which can give grass a yellow or orange hue. However, chlorophyll is the most abundant pigment in grass, so it is the color that we see most prominently.
The amount of chlorophyll in grass can vary depending on the species of grass, the amount of sunlight it receives, and the nutrients it is getting. Grass that gets more sunlight will have more chlorophyll, and therefore will appear greener. Grass that is not getting enough sunlight will have less chlorophyll, and therefore will appear yellow or brown.
The nutrients that grass needs to produce chlorophyll include nitrogen, phosphorus, and potassium. If a grass plant is not getting enough of these nutrients, it will not be able to produce as much chlorophyll, and therefore will appear less green.
So, the next time you see a green lawn, remember that it is all thanks to chlorophyll!