For your photos with the blue uniforms, open them in Camera RAW and adjust the temperature to about a +15 or +18. Or open the photo in Photoshop, add a Photo filter, Warming Filter 85, and set it at about 38%. You'll find your purples.
The D800's auto white balance is pretty amazing but there is still some lighting that challenges it. RAW is one solution. Leraning how to set a custom white balance or using something like a X-Rite ColorChecker may help as well.