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Maybe not the best solution, but might be easier to read. You could use the OpaqueFunction Action to wrap creating your Node. Something like (untested, but the idea will work):

...
from launch.actions import OpaqueFunction

def start_my_executable(context, *args, **kwargs) -> List[LaunchDescriptionEntity]:
    package_path = get_package_share_directory('my_package')
    color_param = context.perform_substitution(LaunchConfiguration('color'))
    config_file_name = 'red.yml' if color_param else 'blue.yml'
    config_file = os.path.join(package_path, 'config', config_file_name)
    return [Node(... , parameters=[config_file])]

def generate_launch_description():
    ...
    launch_description.add_action(OpaqueFunction(function=start_my_executable)