Oh, where to begin? Let me start with 'watered down paint'. 25-50% before the material gets to the site? Impossible. You would basically be painting with water at that point. It would be less of a hassle, and cost, to simply use proper material. You would be forced to apply three coats instead of two, as the coverage would be horrible. Whatever cost you think might be saved in materials would be lost in labor. http://www.youtube.com/watch?v=b6_WEt9k_Hw&feature=kp
Even if you think you'll probably do the job yourself, it's good preparation to seek estimates from professional home painters, whether your painting the exterior or interior of your home. Then you'll have a financial point of comparison and you may benefit from what a home painting contractor has to say about the condition of your home, color choices and types of paint available. Let the painter make his pitch for a professional job before you decide what to do. You can still opt to do it yourself while having learned something worthwhile.
The psychological effect of green is largely dependent on the tone or hue. Some green hues create a positive, natural atmosphere. However, darker hues or pale olive green can seem militaristic or ill. Multiple shades of green can serve different purposes and set different moods. Maritime greens are ideal for studios and offices as they inspire concentration, while cool forest greens can be used in bedrooms and bathrooms.