You must download Pokemon silver, but you can play Pokemon indigo without downloading.
Actually you can go to www.playr.org/search/Pokemon however you won't be able to save unless you regster
Here is another site:gbemul.com/game/289/Pokemon_-_silver_version_(color)/
just type in play Pokemon silver online and it should say play Pokemon silver online at playR
werhe can you play pokemon silver online with saves
Pokemonindigo
playr.com
pokemonbattlearena.net
You need to have Gold for online play. Silver is good for downloading demos and content.
You can Play Pokemon Red,Silver and Gold online with no download by going onto www.playr.org Hope this helps.
In acid play
Just insert it into your DS, no downloading is needed, nor any kind of internet connectivity, unless you want to play online.
go at www.pokemonbattleaerena.com (its still Pokemon crater)
http://www.doperoms.com/
You can play on playr,unova RPG which used to be Pokemon indigo, you can also play on Pokemon tower defence but it's probably only 10% like a Pokemon journey