How about actual rainbow colors?

rainbow.py

@@ -5,12 +5,19 @@ Copyright 2013, sfan5
 """
 import random
 
+rainbowcolors = ["4", "7", "8", "3", "12", "6", "13"]
+#TODO: make this rainbow better (can't really make it that better because IRC colors suck)
+
 def colorize(text):
 	out = ""
+	i = 0
 	for c in text:
 		if c in list(str(i) for i in range(10)):
 			c = u"\u200b" + c # 'ZERO WIDTH SPACE' cuz IRC clients are stupid
-		out += "\x03" + str(random.randint(2, 15)) + c
+		out += "\x03" + str(rainbowcolors[i]) + c
+		i += 1
+		if i >= len(rainbowcolors):
+			i = 0
 	return out
 
 def rainbow(phenny, input):