Previous posts have talked about the cognitive benefits of hiking - walking in nature does a lot more for you than simply burn off calories. When you're walking at your own pace your working memory is better than when you're standing still and that working memory is important for reasoning and learning, for example. Being in daylight also boosts your mood and that makes it more likely that you'll have creative thoughts and get along with your fellow hikers. But there's environmental psych related research that can make your outdoor walks even better.
Recent research by Andrew Elliott and Henk Aarts ("Perception of the Color Red Enhances the Force and Velocity of Motor Output." Emotion, vol. 11) shows that you should probably hike with something red. Their work links seeing red and improved performance on simple strength-related motor activities. The benefits are found with tasks that require short bursts of activity - such as sprinting away from a bear. Red isn't a good choice if you'll be doing something requiring concentration - such as walking on a rope bridge over an abyss.