Adding a black underbelly

I don't know much about editing things on second life. but i want to do this for a friend. I figure this fits the texturing category. Mai friend wants her fox avatar to have a black underbelly. I don't know how. Any ideas? If its complicated. than its probally a lost cause XD

What's your knowledge level at this point? You say you don't know much about how this kind of thing works within SL, but what about RL? Do you have any experience with Photoshop, or any other suitable paint program?

If you already know what you're doing with 2D digital art, then transitioning to texturing for 3D won't be a huge leap for you. If you have no experience at all, though, then you've got a lot to learn, even for such a relatively simple task as the one you described.

Also, how is the fox costume constructed? Is the belly area you're talking about part of the regular avatar avatar body, or is it an attached object? And does your friend have access to source textures that are on it, as well as permission to modify them?

The answers to those questions are all very important.

Most furry avatars don't give you access to modifiable copies of the textures, even when the avatar in general is modifiable. This is because a well-done job of texturing a skin and a set of prims to make a really good looking furry avatar is one of the biggest parts of making an avatar that will sell well. Give away the texturing, and you give away much of their value.

Some avatar makers are willing, for a reasonable fee, to do custom-colored versions of the avatar. So my best advice for you is to ask the maker of the avatar first if that option is open to you. It will get the best results.

If the avatar maker is too busy to do custom work, and they can't recommend an approved source that will do it, then you'll likely have to create your own textures to replace the original ones. What sort of textures these will be, and how they need to be laid out will depend on what parts of the fox avatar's underbelly are on prims, and what parts are on the avatar body as part of the skin.

Modifying the coloration of a furry avatar is a moderately difficult task - not a "beginner's project", certainly. Yet as long as the avatar is modifiable, it can just as certainly be done, with some thought and effort. You need to be good enough with 2D texture creation to match the original textures and colors. You also need to know enough about building and texturing prims to get a good feel for how the texture is applied to the prims that are involved in the areas you want to change.

Another option my simply be to seek a different avatar that comes in the coloration you seek, or that offers color control as an option. I bought a Dire Wolf avatar recently that allowed you to use a HUD control to easily change the color of the base fur, the underbelly, the legs, and the paws. And there are a lot of different furry avatar makers out there who make nice-looking Fox avatars. I've seen just about any color combination you can imagine...