Step 1: Dismantle the LED part of the flashlight
This may be hard, as it's stuck in there, but in the 2 that i've done this two, they aren't glued at all, so it should be easy.
Step 2: Remove the old LEDs
Step 3: Put the Blue LEDs in
side note, ultra bright white LEDs use the same current as ultra bright blue LEDs, green ones will also work, as should violet, and pink LEDs.
Red or yellow will not work.
Step 4: Put the Flashlight back together
see some more pictures heresee some more pictures here