Red flowers, yellow flowers: Which are more precious?

When we send loved ones roses, we send red roses. Why not yellow roses?

In the wildness, most flowers are yellow. Why not red?

I guess it is cheaper for plants to produce yellow flowers. Plants are predominantly green.From the light spectrum, the color yellow is close to green and the color red is more distant to green. Probably it is more difficult for plants to produce the color red than yellow. Red rose is more difficult to produce than yellow rose and hence is more valuable. Unconsciously, we sense that red color is more valuable. Yellow flowers are cheaper to produce and hence they are more abundant.

Most grasses have yellow flowers. Many trees have red flowers. Trees are bigger. Extra cost for red flowers won't be as much burden for trees.