About half a year ago, I looked at a bunch of archived audio files and tried to analyze the frequency. I came up with the following, but I don't have a scanner to confirm any of these frequencies so sorry if they are off. I may have rounded some of the tones off due to fluctuations, so I'll put the exact tone in brackets. I also looked at South Metro's and Littleton's Tones as well, but I'm assuming you just want tones that are dispatched by Douglas County. Enjoy!
Douglas County Dispatch Tones (Elbert County Departments)
TONE A: 675 Hz (1 sec) [673 Hz]
TONE B: 745 Hz (2.3 sec)
Castle Rock Fire Department
TONE A: 350 Hz (1 sec) [349 Hz]
TONE B: 410 Hz (3 sec)
Franktown Fire Protection District
TONE A: 370 Hz (1 sec)
TONE B: 435 Hz (3 sec)
Larkspur Fire Protection District
TONE A: 350 Hz (1 sec) [349 Hz]
TONE B: 370 Hz (3 sec)
Jackson 105 Fire Protection District
TONE A: 370 Hz (1 sec) [367 Hz]
TONE B: 540 Hz (3 sec)