You are describing sedimentary rocks. Sedimentary rocks are formed from the accumulation and compaction of mineral and organic particles in layers (strata). Shale and limestone are indeed examples of sedimentary rocks, while granite is an igneous rock and slate is a metamorphic rock. The color of sedimentary rocks can vary widely depending on their mineral content and the environment in which they formed.
"I am a rock type that is formed from compacted material, usually in strata. Shale and Limestone are examples of me, while Granite and Slate are not. My colour varies."
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