原来 / 本来
Similarities
Both 原来 and 本来 can be adjectives meaning “original” or “former”, and both as adverbs can say the past differed from now.
这是它原来的颜色，不过现在已经穿了好几年，颜色都变了
这是它本来的颜色，不过现在已经穿了好几年，颜色都变了
我家原来住这儿附近，不过这里以前不像现在有这么多楼房
In these sentences 原来 and 本来 are interchangeable.
Difference — 原来
我还以为是谁帮我打扫房间呢，原来是你啊！
Difference — 本来
这本书本来应该昨天还给你，真不好意思
Quick comparison
| 原来 | 本来 |
|---|---|
| it turns out… | originally… / should have… |
| a newly discovered fact | the original plan or expectation |
| expresses realisation | expresses what was supposed to happen |
原来 → a newly discovered fact
本来 → the original situation, plan or expectation