These are tiles that are baked in Raeli Oven. They are a Complex item, in that they are all 'Raeli Tiles', but coming in the same colors defined for paint.
Although the color shown by the Raeli Oven during the baking process changes smoothly, the color the tiles end up when used will be the color corresponding to the name, not the color shown in the color swatch.
If you are in need of Raeli Tiles, but do not have access to an oven (or to an oven that produces the colors you want), browse to the Tile Trading Page.
A Raeli Mosaic is composed of raeli tiles that are broken into useful shapes, then assembled by the artist into (hopefully) pleasing designs.
A Funerary Temple's glory depends on the number and variety of raeli tiles added to it. You can add as many as you care to, but you get diminishing returns immediately. Your quandry, then, is balancing Glory with other uses your tiles can be put to (including trading for colors which might get you MORE glory).