Capturing the fine details and colors of flowers is a great way to challenge yourself when doing macro photography. Certain colors can be difficult to expose when they are at their brightest. The different gradients or tones of yellow are particularly tough to avoid washing out, so I consider it a victory to get great detail in bright sunlight. Orange, and red are also tricky, and if you shoot with manual settings, its a good way to really get a feel for eyeing things out and making adjustments.