“sunshine over a short period of time may increase the risk of suicide but may also lower the risk over several months”
This actually makes sense in view of the discovery of “Blue light receptors” in the eyes that are not wired to the visual area of the brain but instead to the areas that regulate energy, alertness, wakefulness, and mood.
If someone is depressed and suicidal, and experiences a sunny day with blue sky, they may suddenly have the energy to act on the suicidal urges. After a while of sunny weather their depression goes away and the risk of suicide drops.
Keep in mind that white light (sun light) also contains the blue spectrum, and that green is just blue and yellow combined.
Very bright green light probably would have a similar effect.