I was painting in Catalina State Park about mid-day. The values were flattening out and all I was left with were gray or neutral violets and greens (the colors of the desert). Usually with grays at mid-day everything gets washed out, shadows disappear and the lights run together. What helps at times like these is to think of value and temperature first, not color. Your goal should be to think of the value of the large shapes in the landscape and what their angle to the sun is. For example, objects that are upright, trees, cactus, fence posts will catch the least amount of light at mid-day. Shapes or objects that are slanted, hills, rooftops, will catch a little more light, and shapes that are flat like the ground and roads will catch the most light. Knowing the three angles allows me to push the value difference between them which creates more depth. The temperature of these shapes, warm or cool allows me to make objects recede or come or forward in the painting. It also helps me to determine the color. If I'm thinking value first, how dark or light an object is, then whether it's warm or cool, then it's easier to determine the local color. The value and termperature will be more important because they determine the type of light in the painting, which for me is the whole reason for painting.