popup.js

let changeColor = document.getElementById("changeColor");

chrome.storage.sync.get("color", ({
    color
}) => {
    changeColor.style.backgroundColor = color;
});


changeColor.addEventListener("click", async () => {
    let [tab] = await chrome.tabs.query({
        active: true,
        currentWindow: true
    });

    chrome.scripting.executeScript({
        target: {
            tabId: tab.id
        },
        function: setPageBackgroundColor,
    });

    console.log('test');

});

// The body of this function will be executed as a content script inside the
// current page
function setPageBackgroundColor() {
    chrome.storage.sync.get("color", ({
        color
    }) => {
        document.body.style.backgroundColor = color;
    });
}