You can find Jopsy's Particle Lab here.

//// "Light" EFFECT TEMPLATE v1 - by Jopsy Pendragon - 4/8/2008
//// You are free to use this script as you please, so long as you include this line:
//** The original 'free' version of this script came from THE PARTICLE LABORATORY. **//

// SETUP:  Use with particle lab Controller Templates to activate/deactivate.

// Causes the prim to emit light, illuminating nearby avatars, prims and ground.

// Customize the particle_parameter values below to create your unique 
// effect and click SAVE.  

// PURPOSE:  This script will enable/disable and adjust the LIGHT emitted by a prim.

// NOTE:  This is not a particle effect.

vector color = <1.00,1.00,1.00>; // red, green and blue values 0.00(dark) to 1.00(bright)
float intensity = 1.00;  // % brightness:  0.0 to 1.0
float    radius = 5.00;  // range/distance of light:  0.0 to 20.0 meters
float   falloff = 0.5;  // % brightness at max distance 0.00 to 1.00



string  CONTROLLER_ID = "A"; // See comments at end regarding CONTROLLERS.
integer AUTO_START = TRUE;   // Optionally FALSE only if using CONTROLLERS.

rotation adjustment = ZERO_ROTATION;

default {
    state_entry() {
                
        if ( AUTO_START ) 
            llSetPrimitiveParams( [PRIM_POINT_LIGHT, TRUE, color , intensity, radius, falloff]);
        
    }
    
    link_message( integer sibling, integer num, string mesg, key target_key ) {
        if ( mesg != CONTROLLER_ID ) { // this message isn't for me.  Bail out.
            return;
        } else if ( num == 0 ) { // Message says to turn particles OFF:
            llSetPrimitiveParams( [PRIM_POINT_LIGHT, FALSE, ZERO_VECTOR , 0.0, 0.0, 0.0 ]);
        } else if ( num == 1 ) { // Message says to turn particles ON:
            llSetPrimitiveParams( [PRIM_POINT_LIGHT, TRUE, color , intensity, radius, falloff]);
        } else { // bad instruction number
            // do nothing.
        }            
    }
        
}

// for more visit:

// http://rpgstats.com/wiki/index.php?title=LlSetPrimitiveParams
// http://wiki.secondlife.com/wiki/LlSetPrimitiveParams
// http://lslwiki.net/lslwiki/wakka.php?wakka=llSetPrimitiveParams