Knowing the background is going to be mostly yellows/browns/greens, it makes sense to wear (OPTION 1) bright colors like blues, yellows, reds, oranges, or anything that will pop. Outfit OPTION 2 … it works to wear colors that compliment the scene… like light gray, whites, tan, or soft colors. I do not recommend matching but it works to be in similar tones and textures. In the end it is up to you! Extended photography tips: http://www.renditionstudios.com/renditionstudios.com/Photo_Shoot_Tips.html
Should you want to take this a little further… look online and take note of the “look” you like and try and emulate that.
Family Photography gallery: http://coloradoportraitphotography.com/_Featured_Families.html
Children only gallery: http://coloradochildrensphotography.com/_Featured_Children.html
Babies only gallery: http://coloradochildrensphotography.com/_Featured_Babies.html
Individual Portraits: http://coloradoportraitphotography.com/_Featured_Individuals.html