most plant stretch can be managed by making sure the temp diff between lights on and off (vDiff) is not to far apart. Shrinking the temp so there is no change will stop all stretch in 99 plants out of 100. It relates to turgor pressure, you need enough to push the nutes to the tips, but big swings will mean she goes up and out :)
Light., is more to do with location for a plant, so it measures the ratio of red to far red and knows which parts are shaded our not, this is how plants see. Red equals good solid light hitting leaves dark red means more shade from a plant perspective, Not over populating grow rooms will also help prevent too much stretch.
it is true blue light can stop plants reaching, but most growing occurs when lights are out, Controlling temps is a better option imo