Update field data table and configuration storage object.

module_name.install

<?php


/**
 * Update field data table and configuration storage
 */
function _update_field_data(
    $entityType,
    $field,
    $valueMapping,
    $configOverride
) {
    $tables = [
        $entityType.'__' . $field,
        $entityType.'_revision__' . $field,
    ];

    foreach ($tables as $table) {
        foreach ($valueMapping as $currentValue => $newValue) {
            Database::getConnection()
                ->update($table)
                ->fields([$field . '_value' => $newValue])
                ->condition($field . '_value', $currentValue)
                ->execute();
        }
    }

    \Drupal::configFactory()
        ->getEditable('field.storage.'.$entityType.'.'.$field )
        ->set(
            $configOverride['key'],
            $configOverride['value']
        )
        ->save();
}

function module_name_update_N() {
    $field = 'field_overlay_color';
    $entityType = 'paragraph';
    $valueMapping = [
        'None' => 'purple',
        'Pink' => 'purple',
        'Black' => 'purple',
        'Purple' => 'purple',
        'Magenta' => 'magenta'
    ];
    $configOverride = [
        'key' => 'settings.allowed_values',
        'value' =>[
            [
                'value' => 'purple',
                'label' => 'Purple',
            ],
            [
                'value' => 'magenta',
                'label' => 'Magenta'
            ],
            [
                'value' => 'maroon',
                'label' => 'Maroon'
            ]
        ]
    ];

    _update_field_data(
        $entityType,
        $field,
        $valueMapping,
        $configOverride
    );
}