blue led flasher?

Red LEDs are usually 1.7V whereas blue can be twice that (3.2-3.4V) hence with the Red's dropping resistor you are getting half the current (ie, 10mA instead of 20mA). But if you put your blue LED across 12V & GND and it didn't blow up. I suggest it has its own resistor as well. Then there is the simple optical explanation - we are much less sensitive to blue than to red. Typically blue need to be 2 to 3 times the "power" to have the same intensity as red. Let me know which of the above does NOT apply in this case.

Try wiring two blue leds in series..and depending on the length of the wires, make sure the further they travel, the lower the gauge wire. I am gonna guess 16g. Wiring in series would mean connecting one red lead and one black lead to the alarm brain from each led, and wire the remaining black and red wires together between the two. Let me know how it works out if it does.

If you wired the blue LEDs* from a 12volt constant source to either the ignition, acc or the alarms GWA wire, you will get the desired result, what you won't get depending on the alarm is zone or tripped reporting. *Assuming you test as Oldspark recommended and they are 12volt compatible. Most "better" alarms drive their LEDs with approx 2-3.5 volts, after markets, esp flashers tend to have inbuilt resistors to run directly off 12 volts. Also most modern units again the "better quality" alarms now run blue LEDs so the question's moot any way.

You can drive a transistor off of the LED output to amplify the current. You will need to know which leg of the LED output is the switch leg so you know which pin to hook the transistor up to. If the ground is switching you'll need a PNP transistor if the + is switching you'll need an NPN transistor. You should be able to find a general purpose transistor drive circuit on Google.Kevin Pierson