In general it is believed that green is a relaxing colour, but I wanted to counter this superficial categorisation with a quote from Frutero & Luccentini’s "Enigma in un luogo di mare" (Mystery in the Pine Forest).
In this novel, the main character often has to go through the pine forest with 18.300 pines and at the same time he calculates how many potential murderers are hiding behind the trees.

In a pause for thought in our office, looking at the pictures, I meditate on what in my current task is an imagined problem and where something I had not thought of will possibly appear from nowhere.
Besides, the book is highly recommendable.