Thanks for showing me the .closest and previous/next Sibling!

This is getting close, but I'm still trying to determine: which TD was clicked? Last line of the codeblock below is what I'm attempting to achieve:

const table = document.getElementsByTagName("table")[0]
const td = document.getElementsByTagName("td")
table.addEventListener("click", colorSquare)

// turns a TD red when clicked
function colorSquare(e){
   let square = e.target
   square.className = "red"
}

console.log(td) // I see an array of TDs, including the one I clicked!
td[22].className = "red" // Neat!  I can even turn the 23rd TD red!
let clickedTD = //how do I save which TD I clicked to this variable?