There are many, many different types of substrate to use which can range from a more natural color to now highly vivid colorations. Which type of substrate do you prefer to keep inside of your setups and why? Is it to keep with a theme that you may have going on, or is to match/complement the colors of the livestock that you plan on keeping inside?
I always try to match them with the colors of the livestock. Rarely I would go for complementing colors.
I do like using colored stones the most.