I have a custom entity ‘myentity’ with some fields, and one of them is a taxonomy field with the next definition:

 $fields['colors'] = BaseFieldDefinition::create('entity_reference')
                ->setLabel(t('Colors'))
                ->setDescription(t(''))
                ->setRequired(FALSE)
                ->setSetting('target_type', 'taxonomy_term')
                ->setSetting('handler', 'default:taxonomy_term')
                ->setSetting('handler_settings',
                        array(
                            'target_bundles' => array(
                                'colors' => 'colors'
                    )))                
                ->setDisplayOptions('view', array(
                    'label' => 'above',
                    'type' => 'author',
                    'weight' => 0,
                ))
              ->setDisplayOptions('form', [
                    'type' => 'options_select',
                    'weight' => 0,
                ])
                ->setDisplayConfigurable('form', TRUE)
                ->setDisplayConfigurable('view', TRUE);

It works good and I can use my entity without any problem. But there is a problem:

FieldStorageConfig::loadByName('myentity','colors');

returns NULL.

I don’t know why, but I think It should returns my field definition.
Because It doesn’t work, I have tried with "drush upe" (with this module) that let you ensure the field definition is right, but without success.