cascade doesn't support isHexColor

```
const isColor =  t.cascade (t.isHexColor({ alpha: true }))

```

```
Argument of type 'LooseValidator<string, string>' is not assignable to parameter of type 'AnyStrictValidator'.
  Type 'LooseValidator<string, string>' is not assignable to type 'StrictTest<any, any>'.
    Signature '(value: string, test?: ValidationState | undefined): boolean' must be a type predicate.
```