Yes pink is darker than green and orange
Yes orange is darker than light blue.
Yes, red is generally darker than orange. Red has a longer wavelength and thus appears darker than orange, which is a lighter and brighter color.
Yes red is darker than green.
When you mix green and orange and yellow, you get a muddy brown color. The combination of these three colors results in a darker, earthy tone rather than a vibrant hue.
Yes orange is better than green
If you mix pigments (not light) that are green and orange you will get a grayish brown. Depending on the quantity and quality of the pigments and their hues you might get anything from darker green to gray to brownish orange,
Other way around
The orange would appear darker or muted under green light, as green light will absorb some of the orange wavelengths. This interaction between the two colors may result in the orange appearing more brownish or dull.
It's a darker orange than the original.
Yellow can be mixed with the colors on each side of yellow on the color wheel - orange and green, but beware - it will be a very dull yellow, and probably darker in value than you want. This is why, in painting, yellow is a primary color. It is a very intense color of very light value. The colors you would try to mix it from - orange and green - are both darker in value and less intense. This is why the resulting mix is darker and duller than primary yellow. So if you want a light, bright yellow, you won't be able to mix it using paint.
Brown is the more darker color because of its texture. Just like a tree is darker than grass.