The processed human hair used to make hair systems goes through a process which strips some of the cuticle from the hair, therefore it reflects certain wavelengths of light slightly differently than your natural bio hair (which has it's natural cuticle intact) reflects them... especially some types of bright flash and fluorescent lighting.

My hair always looks similar to yours under direct fluorescent lighting, but I gladly accept that small flaw since I know my replacement hair looks absolutely fantastic 99% the rest of the time.

Your hair should look fine under most lighting conditions to the human eye and will probably look OK in most photos too, since a flash will rarely, if ever, be positioned that close to your head during normal circumstances when someone else is taking your picture.

Using some Back2Natural conditioner can help dull this effect, as Paul suggested. Using a little product (gel and/or wax) might help too. Try out some different types to see which ones work best.