Here's what we know:
* Descriptions: Contemporary descriptions from the time often describe him as having "dark hair" or "black hair".
* Photographs: While the famous photo of Kelly in his armor is blurry, some experts believe it shows dark hair.
* Family history: His family lineage suggests he likely had dark brown hair.
However, there are some accounts mentioning "red hair" or "sandy hair," possibly due to the sun bleaching his hair or misinterpretations.
Ultimately, the exact color of his hair remains a mystery, but dark brown seems the most likely.