There is perhaps no better way to fake texture than to add color gradations. In straight hair, color can create depth, and depth can create a sense of fullness. It can make straight hair look lively.
For depth, don't go with a monotone. Go with highlights (lighter tones) and low-lights (darker tones).
But be careful, because if your hair is very straight (and you wear it very straight), highlights can end up looking streaky and cheap. So talk to your hair stylist about it. You may find it more natural looking to go only with low-lights.
No matter how you wear your straight hair, the surest way to make it look great is to care for it. That means good conditioner, gentle brushing, low heat and minimal use of the curling iron. That thing can really fry your hair.
For more information on straight hair, hair care and related topics, look over the links on the next page.