Magento 2 – How to Change Color of Cart Icon in Minicart

I finally got it working.

The problem was, that form I was creating in js wasn't appended to body.

Here you have request sended via js:

var url = '/modextend/cart/addProducts/';

if(selectedAccessories.length === 0)
{
    return false;
}

var form = $('<form>').attr('action', url).attr('method', 'post');
var input = $('<input type="hidden" name="products_ids" />').val(selectedAccessories.join(','));
input.appendTo(form);

form.appendTo('body').hide().submit();

appendTo('body') is here critical part.

And in controller standard redirect to cart:

$products = $this->getRequest()->getParam('products_ids');
$resultRedirect = $this->resultRedirectFactory->create();

if($products)
{
    $products = explode(',', $products);

    try {
        $this->cart->addProductsByIds($products);
        $this->cart->save();

        $this->messageManager->addSuccess(__('Selected accessories has been added to your cart.'));
    } catch (LocalizedException $e) {
        $this->messageManager->addException(
            $e,
            __('%1', $e->getMessage())
        );
    } catch (\Exception $e) {
        $this->messageManager->addException($e, __('There was an error while adding accessories to your cart.'));
    }
}

$resultRedirect->setPath('checkout/cart/index');

return $resultRedirect;

Create your theme on below path given instead of vendor folder

app\design\frontend\vendor\themename

and apply theme from admin and clear cache, whenever you add new files in your theme you need to deploy static content from cmd command given below.

php bin/magento setup:static-content:deploy