script.js

const reset = document.getElementById("reset_button")
const change = document.getElementById("change_button")

reset.addEventListener("click", resetGrid)
change.addEventListener("click", changeColor)

function resetGrid() {
    for (let i = 1; i <= 9; i++) {
        const gridItem = document.getElementById(i)
        gridItem.style.backgroundColor = "transparent"
        console.log(gridItem)
    }
}

function changeColor() {
    const blockId = document.getElementById("block_id")
    const colorId = document.getElementById("colour_id")

    if (!blockId.value) {
        alert("Please enter block id")
    }
    if (!colorId.value) {
        alert("Please enter colour id")
    }
    resetGrid()

    const gridItem = document.getElementById(blockId.value)
    gridItem.style.backgroundColor = colorId.value

    blockId.value = ""
    colorId.value = ""
}