fold1.vl

{
    "transform": [
        {
            "as": [
                "k",
                "v"
            ],
            "fold": [
                "gold",
                "silver"
            ]
        }
    ],
    "mark": "bar",
    "data": {
        "values": [
            {
                "silver": 20,
                "country": "USA",
                "gold": 10
            },
            {
                "silver": 26,
                "country": "Canada",
                "gold": 7
            }
        ]
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "encoding": {
        "color": {
            "field": "country",
            "type": "nominal"
        },
        "x": {
            "field": "country",
            "type": "nominal"
        },
        "column": {
            "field": "k",
            "type": "nominal"
        },
        "y": {
            "field": "v",
            "type": "quantitative"
        }
    }
}