At the moment, there is only one type of polished granite available in Minecraft Bedrock Edition. However, a mod called More Polished Granite Colors addresses this flaw. After you install More Polished Granite Colors in Minecraft Pocket Edition, you will have as many as 115 blocks at your disposal!
The mod works in Minecraft for the phone on new versions. For all blocks to be “functional”, be sure to enable experimental gameplay capabilities. Enjoy your survival and construction in Minecraft on your tablet!