A bit more on how this library is using Timer1 and Timer2 to run GSCLK and BLANK:
The PWM on the TLC5940 works by counting the number of GSCLK pulses; a setting of 2048 will mean the LED stays on for 2048 pulses and then turns off for the rest of the cycle. After 4096 pulses, the counter needs to be reset by a pulse on BLANK. In the library, I'm using Timer2 to generate the GSCLK pulses and Timer1 to generate the BLANK pulse.