If memory serves, a Rainbow Pokeblock will increase all 5 Contest conditions simultaneously by an equal amount. An Indigo Pokeblock will raise Beauty by a LOT, and one or both of the adjacent conditions by a little bit.
There will always be 2 flavors present in an Indigo PokéBlock.
The first, largest flavor will be Dry (for beauty)
The second can be any flavor on the spectrum, and will have a strength of fifty or less.
Hope this helps.