Customize highlight-words

Question

I want to change default highlight color of highlight-words from vscode.

This is the default settings.json

{
...
    "hexeditor.defaultEndianness": "little",
    "hexeditor.inspectorType": "aside",
    "highlightwords.colors": [

        {
            "light": "#b3d9ff",
            "dark": "red"
        },
        {
            "light": "#e6ffb3",
            "dark": "orange"
        },
        {
            "light": "#b3b3ff",
            "dark": "yellow"
        },
        {
            "light": "#ffd9b3",
            "dark": "magenta"
        },
        {
            "light": "#ffb3ff",
            "dark": "cornflowerblue"
        },
        {
            "light": "#b3ffb3",
            "dark": "cottoncandy"
        },
        {
            "light": "#ffff80",
            "dark": "green"
        },
        {
            "light": "#d1e0e0",
            "dark": "red"
        }
    ]
}

What is the meaning of "light" and "dark" in the json code above?