Colorschemes can be written specifically for gvim, or specifically for an 88/256 color terminal. If your terminal does not support 88 or 256 colors -- or your colorscheme doesn't support terminals at all, many colorschemes are not going to work.
If you are willing to give it a try the CSApprox.vim script will attempt to make gui colorschemes available in your terminal by changing the colorscheme to use colors that are available in your terminal.
Another option is to use the CSExact.vim script which instead changes your terminal's color palette to match the colors defined in the colorscheme. This has the advantage of being more precise with the few drawbacks mentioned in the docs.