Green is a colour associated with nature. All the chlorophyll in plants and trees that captures solar energy, also has a pleasant effect on our mood. Green is said to be a calming colour.

Research has shown that people who work in offices overlooking a park or trees are more satisfied and calm. People who worked in offices surrounded by concrete buildings, found improved mood after transfer to offices overlooking greenery.
Accessibility to green spaces is also important. The calming effect is more profound if the greenery is accessible to people. Having the knowledge that one can visit that lovely park next to one’s office anytime after work, itself soothes the mind.
One could always try to create small green spaces within the office. A little bit of imagination and work could lead to a relaxing green space in the midst of all office clamour. Having few potted plants with an artificial grass mat in an office corner can work wonders.
This is the reason why many companies are creating rooftop or terrace gardens. Lowering stress levels in employees, increases the efficiency and teamwork. The colour green can therefore reduce a lot of office stress and tension. In places such as hospitals, plants are replaced by pictures of nature. Pictures of flowing rivers with lush green forests, tend to evoke a similar soothing effect.
In case none of this is possible, one could always go on weekend trips to relax in the midst of greenery.