Fixed CSS transparency bug in _style_properties.py

Author: edward-jazzhands

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased
+
+### Fixed
+
+- Fixed issue with the "transparent" CSS value not being transparent when set using python
+
 ## [3.5.0] - 2025-06-20
 
 ### Changed

src/textual/css/_style_properties.py

@@ -984,6 +984,7 @@ def __set__(self, obj: StylesBase, color: Color | str | None) -> None:
                     continue
                 try:
                     parsed_color = Color.parse(token)
+                    _r, _g, _b, alpha, _, _ = parsed_color
                 except ColorParseError as error:
                     raise StyleValueError(
                         f"Invalid color value '{token}'",