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
@@ -82,29 +82,30 @@
   return tinycolor(`#${color}`).isDark();
 }
 
-const selectedThreadColors = [
-  'B8753D',
-  'C85000',
-  'AA4B4B',
-  '4B87AA',
-  '648CAA',
-  '57697F',
-  '6D49AB',
-  '00A591',
-  '008F83',
-  '575757',
-];
+const selectedThreadColors = {
+  'B8753D': 1,
+  'C85000': 2,
+  'AA4B4B': 3,
+  '4B87AA': 4,
+  '648CAA': 5,
+  '57697F': 6,
+  '6D49AB': 7,
+  '00A591': 8,
+  '008F83': 9,
+  '575757': 10,
+};
+export type SelectedThreadColors = $Keys<typeof selectedThreadColors>;
 
 function generateRandomColor(): string {
-  return selectedThreadColors[
-    Math.floor(Math.random() * selectedThreadColors.length)
-  ];
+  const potentialColors = Object.keys(selectedThreadColors);
+  return potentialColors[Math.floor(Math.random() * potentialColors.length)];
 }
 
 function generatePendingThreadColor(userIDs: $ReadOnlyArray<string>): string {
+  const potentialColors = Object.keys(selectedThreadColors);
   const ids = [...userIDs].sort().join('#');
-  const colorIdx = stringHash(ids) % selectedThreadColors.length;
-  return selectedThreadColors[colorIdx];
+  const colorIdx = stringHash(ids) % potentialColors.length;
+  return potentialColors[colorIdx];
 }
 
 function threadHasPermission(