Check that each Color field has a color value (format string "#FFFFFF")

I have task: "Check that each Color field has a color value (format string "#FFFFFF")".

I have a solution:

@Test
public void sixTest() {
    Specification.installSpec(Specification.requestSpec(), Specification.responseSpec());
    Response response = given()
            .when()
            .get("https://reqres.in/api/unknown")
            .then()
            .log().all()
            .extract().response();

    ResponseBody body = response.getBody();
    String bodyAsString = body.asString();
    Assert.assertEquals(bodyAsString.contains("#"), true, "Response body contains #");

}

I think I solved the problem incorrectly is there a more suitable solution?

Additional information: The URL https://reqres.in/api/unknown is public and returns e.g.

{
    page: 1,
    per_page: 6,
    total: 12,
    total_pages: 2,
    data: [
    {
    id: 1,
    name: "cerulean",
    year: 2000,
    color: "#98B2D1",
    pantone_value: "15-4020"
    },
    {
    id: 2,
    name: "fuchsia rose",
    year: 2001,
    color: "#C74375",
    pantone_value: "17-2031"
    },
    ...

This problem can be solved using regular expressions

ResponseBody body = response.getBody();
String bodyAsString = body.asString();

//Regexp for a HEX color
String patternString = "#[a-zA-Z0-9]{6}"

Pattern pattern = Pattern.compile(patternString);
Matcher matcher = pattern.matcher(text);

//Check that the text matches the regular expression
boolean matches = matcher.matches();

You can experiment with regular expressions here