From the EIA, regular grade gasoline average price is currently $2.367, while diesel is $2.944, thus diesel 24.4% higher. A diesel truck has to get 24.4% better mileage simply to 'pay' for the increased fuel costs.
EPA estimated mileage for the V6 gas Colorado is 26 MPG, so a diesel would have to earn an EPA average of 32.3 MPG just to break even on the fuel. This seems pretty unlikely given the DPF and other emissions stuff modern diesels are saddled with.
Add in increased maintenance and purchase price and it is probably a losing bet. On the plus side, a diesel should go farther before requiring a rebuild, but new gassers go a long time too. You will recoup some of the increase in purchase price when selling, but it is not going to substantially sway the payback.
Economically, you make a good case. For me, the torque of a good diesel makes the driving experience, cost be damned
