I've only tried a couple different methods myself. I've read about probably hundreds of builds, but that's not quite the same as actually doing it myself.
I think if you are coating something (stryofoam, great stuff, gorilla glue, etc.) with silicone, and working in something (I've usually heard of people using peat, but I imagine you could use broken up tree fern fibers), the color of the silicone probably wouldn't matter too much, if it were me, I'd probably go with whatever is cheapest (I'm assuming window/door clear?).
Then again, if the stuff for texture manages to break off, black silicone would probably be less noticeable then clear, and unless it's significantly more expensive, or you are doing a really huge paludarium, the cost increase probably wouldn't matter much.
When I mentioned treefern fiber, I meant the actual slabs of it - you can get it in 'boards' that are ~1" thick or so, pretty much like they took a tree fern, and cut it up like a regular tree for lumber. It doesn't look great by itself (though, it doesn't quite look horrible either...), but stuff (ferns, mosses, epiphytes) grow on it pretty well, and it's light and easy to work with. I've also heard that a lot of times it will spontaneously grow tropical moss, but not something I've witnessed myself, so...
People do use the broken-up fibers for various things, as components of mixes, etc., but I think if you are looking for something to mix in with silicone, it's probably better to go with something smaller-grained, like peatmoss or something (plus, it's cheaper...)
And as greenman857 said, you can do a really nice looking build without an intensive background/hardscape. Well positioned rocks and driftwood and stuff can provide a lot of 'terrestrial' space that looks really nice. Some of it depends on what you want to put in your pal/viv. If you don't plan on having any primarily terrestrial critters, most plants can do just fine in little 'pockets', and most aquarium plants will grow out of the water if given a chance.
Anyways, whatever method you decide to go with, give it a chance, vivs/pals look best once they've had some time for the plants to grow in, and I think they are what really makes a viv/pal look amazing.