Some users are still stuck at Purple-colored (space) screen when jailbreaking iPhone 4, 3GS, iPod touch or iPad using JailbreakMe 2.0.The problem is caused because of cache which needs to be cleared before you can jailbreak your device.
The steps are given below.
Step 1: Navigate to Settings –> Safari and then clear out History, Cookies and Cache.
Step 2: Reboot your iOS device by turning it off, and then back on.
Step 3: Now try http://jailbreakme.com or http://jailbreakme.modmyi.com again.
It should work now.
You may use JailbreakMe.us.