diff --git a/color.py b/color.py
index 9d0ce7c36..03fb65537 100644
--- a/color.py
+++ b/color.py
@@ -14,6 +14,7 @@
 
 import os
 import sys
+from typing import Optional
 
 import pager
 
@@ -84,7 +85,7 @@ def _Color(fg=None, bg=None, attr=None):
 DEFAULT = None
 
 
-def SetDefaultColoring(state):
+def SetDefaultColoring(state: Optional[str]) -> None:
     """Set coloring behavior to |state|.
 
     This is useful for overriding config options via the command line.
@@ -97,9 +98,9 @@ def SetDefaultColoring(state):
     state = state.lower()
     if state in ("auto",):
         DEFAULT = state
-    elif state in ("always", "yes", "true", True):
+    elif state in ("always", "yes", "true"):
         DEFAULT = "always"
-    elif state in ("never", "no", "false", False):
+    elif state in ("never", "no", "false"):
         DEFAULT = "never"
 
 
diff --git a/tests/conftest.py b/tests/conftest.py
index a13edd7af..ce3c3d6ce 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -18,6 +18,7 @@ import pathlib
 
 import pytest
 
+import color
 import platform_utils
 import repo_trace
 
@@ -28,6 +29,16 @@ def disable_repo_trace(tmp_path):
     repo_trace._TRACE_FILE = str(tmp_path / "TRACE_FILE_from_test")
 
 
+@pytest.fixture(autouse=True)
+def restore_default_coloring() -> None:
+    """Force disable color for reproducible test behavior.
+
+    The few tests that cover color behavior can still reset/change the color as
+    needed.
+    """
+    color.SetDefaultColoring("never")
+
+
 # adapted from pytest-home 0.5.1
 def _set_home(monkeypatch, path: pathlib.Path):
     """