如何更改附加元素的颜色？

I created a "custom append" function that taking in two parameters and appending their's value in a one line. I need to make the first parameter's value to append in a gray color but the second value have to stay as it is. I tried to use a "css(property, name)" function but it didn't work. Where is my fallacy and how to get a needed result?I created a "custom append" function that takin