I have just got a better way to print white decals. I bought an ALPS printer.
I tried and succeeded the decals in white on 2 SD40-2 locos I had that were undecorated.
(And hopefully I got the picture links right!)
If you are going to do any further SD40-2s, you might note that the number is centred under the cab window, unlike the SD70ACe where the number is offset towards the rear of the cab. On the SD40, the "cross" on the white lines is at the front corner of the cab and the battery box/step. Otherwise the models look quite good.
For the original poster, there is no need to repaint locomotives in HO. Bachmann make an SD40-2 and a GE CM40-8M fully painted and lettered in the BHP bubble scheme. I have an SD40-2 which I have run with my DC only BLI AC6000 with no problems. I have a CM40-8M but I haven't tested it yet. It looks good and I have another Dash 8 chassis to use if there's a problem.
Also, BLI have just released SD40-2s in both bubble and the IC&E style blue with a yellow stripe. I have one of those, but since it is only available as a DCC+sound unit, it can't run with the DC only AC6000. The three BHPB units 3078 to 3080 have no lettering apart from the black cab numbers. That's the one problem with the BLI unit, it has blue numbers...
So with the two colour schemes there are six different units available from Bachmann and BLI, with different numbers on some of the BLI units.
There is a good photo of the BLI SD40-2 unit at:http://cs.trains.com/mrr/f/88/p/211365/2318918.aspx#2318918
Strangely enough, it also shows a BHPB model relettered for a US Railroad, which must be some sort of record.