Is there a site to import colors and textures to import into current pallets? Thanks.
You can create your own colors by simply editing existing ones. As for textures, you can find them in the 3D Warehouse, even scavenge textures off of models there or there are numerous websites that offer images you can download and import into SketchUp to use as texture. See SketchUp Texture Club among many others. You could also use your own photos if you want.
It isn’t really a good idea to add materials into the current collections. Instead you can make your own custom collections. You can create a number of collections based on the types of materials you have. I make my own wood textures and sort them by species.