Hersute is correct. Samples from various areas of your head is helpful. There can be more 'tones' to you hair than you realize. The sunlight affect that you describe is exactly why synthetic hair doesn't cut it. Synthetic hair looks great in your hand--it's extremely realistic. But mix it with your own human growing hair and step out into the sunlight and the difference is a dead giveaway. The factory will match your hair color exactly under a microscope.
John