diff --git a/lib/shared/thread-utils.js b/lib/shared/thread-utils.js
--- a/lib/shared/thread-utils.js
+++ b/lib/shared/thread-utils.js
@@ -82,18 +82,23 @@
   return tinycolor(`#${color}`).isDark();
 }
 
-const selectedThreadColors = [
-  'B8753D',
-  'C85000',
-  'AA4B4B',
-  '4B87AA',
-  '648CAA',
-  '57697F',
-  '6D49AB',
-  '00A591',
-  '008F83',
-  '575757',
-];
+const selectedThreadColorsObj = {
+  'B8753D': 1,
+  'C85000': 2,
+  'AA4B4B': 3,
+  '4B87AA': 4,
+  '648CAA': 5,
+  '57697F': 6,
+  '6D49AB': 7,
+  '00A591': 8,
+  '008F83': 9,
+  '575757': 10,
+};
+
+const selectedThreadColors: $ReadOnlyArray<string> = Object.keys(
+  selectedThreadColorsObj,
+);
+export type SelectedThreadColors = $Keys<typeof selectedThreadColors>;
 
 function generateRandomColor(): string {
   return selectedThreadColors[