Protractor - How to store the value of browser.executeScript in variable?

I am trying to store the value of browser.executeScript inside a local variable in my it block but I am not able to do so in all the cases it displays null.

I have tried many ways so far

browser.executeScript('$("#txtName").css("border-left-color");').then(function (color) {
    console.log("This is color" + color);
});

Also this

function returnColor() {
    var a = browser.executeScript('$("#txtName").css("border-left-color");');
    return a;
}

function getColorCode() {
    var a = returnColor().then(function(list) {
        console.log("Output is ***************" + list);
        return list;
    });

    return a;
}

I am using this inside my spec as

   iit('', function() {        
    
             browser.executeScript('$("#txtName").css("border-left-color");').then(function (color) {
                console.log("This is color" + color);
            });
    
            returnColor();
    
    
        });

Will really appreaciate it someone can tell me how to do it properly?

You need to have a return from the script:

function returnColor()
{
    return browser.executeScript('return $("#txtName").css("border-left-color");');
}

Note that you can also solve the same problem via getCssValue():

var elm = element(by.id("txtName"));
elm.getCssValue("border-left-color").then(function (color) {
    console.log(color);
});