Align label color tests with points/shapes conventions

Replace the 3 ad-hoc tests (color_name, hex, rgba_tuple) with 4 tests
that mirror the existing points and shapes pattern: rgba_array, hex,
hex_with_alpha, and alpha_overwrites_opacity_from_color.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: timtreis

tests/_images/Labels_can_color_by_color_name.png

@@ -84,14 +84,17 @@ def test_plot_can_stack_render_labels(self, sdata_blobs: SpatialData):
             .pl.show()
         )
 
-    def test_plot_can_color_by_color_name(self, sdata_blobs: SpatialData):
-        sdata_blobs.pl.render_labels("blobs_labels", color="red").pl.show()
+    def test_plot_can_color_by_rgba_array(self, sdata_blobs: SpatialData):
+        sdata_blobs.pl.render_labels("blobs_labels", color=[0.5, 0.5, 1.0, 0.5]).pl.show()
 
     def test_plot_can_color_by_hex(self, sdata_blobs: SpatialData):
-        sdata_blobs.pl.render_labels("blobs_labels", color="#ff0000").pl.show()
+        sdata_blobs.pl.render_labels("blobs_labels", color="#88a136").pl.show()
 
-    def test_plot_can_color_by_rgba_tuple(self, sdata_blobs: SpatialData):
-        sdata_blobs.pl.render_labels("blobs_labels", color=(1.0, 0.0, 0.0, 0.5)).pl.show()
+    def test_plot_can_color_by_hex_with_alpha(self, sdata_blobs: SpatialData):
+        sdata_blobs.pl.render_labels("blobs_labels", color="#88a13688").pl.show()
+
+    def test_plot_alpha_overwrites_opacity_from_color(self, sdata_blobs: SpatialData):
+        sdata_blobs.pl.render_labels("blobs_labels", color=[0.5, 0.5, 1.0, 0.5], fill_alpha=1.0).pl.show()
 
     def test_plot_can_color_labels_by_continuous_variable(self, sdata_blobs: SpatialData):
         sdata_blobs.pl.render_labels("blobs_labels", color="channel_0_sum").pl.show()