Edit in JSFiddle

var app = angular.module("app",[]);

app.controller("ColorController", function($scope){   
	$scope.convert = function(){
        $scope.hex =("#").concat(Math.floor((Math.random() * 10000) + 1))
    }
})

app.directive("color", function() {
    return {
        restrict: 'E',
        scope: { do: '&' },
        template: '<input type="text" ng-click="do()" /> {{hex}}'
    }
});
<div ng-app="app">
    <div ng-controller="ColorController">
        Renk-1 <color do="convert()"></color>{{hex}}<br/>
    </div>
</div>