You can purchase striping as decals (Champ and perhaps Microscale) or dry transfers (C-D-S), but you may find the choice of colours limited to white, black, red, or gold/yellow. These are available in several widths, but are only straight lines. There are some sets available for specific railroads or locos that may contain the colours or curves/shapes that you need. Don't overlook diesel lettering sets as a source of striping/lining, especially cab unit sets, for the early, and usually, most complicated paint and lettering schemes.
This loco was striped using dry transfers from C-D-S:
This loco used decal striping from a set for a CPR steamer, and the same style striping is also available from C-D-S, as dry transfers. The decals are the easiest to use, as you can reposition them during installation. With dry transfers, you get one chance only.
You can also paint on the striping, but need to be proficient at making and applying masking and at applying the paint.
Not much skill involved in this one. The secret to keeping the spacing between the light (which was applied first) and dark is to cut the masking for the entire length of the striping, including the spaces that will be painted the darker colour. For this loco, I started with two pieces of masking tape, applied one atop the other, on a sheet of glass. Using a new blade and a straightedge, I removed both factory edges of the tape, using dividers to ensure that both ends of the remaining strip were the same height. I then used a square and ruler to trim the ends, making the strip the same length as that of the hood of the loco. Using dividers, the stripes were layed out and cut through the tape: the first piece, used only as a spacer to position the mask for the first white stripe, was the small wedge-shaped piece immediately behind the cab. Basically, the entire precut strip of masking tape was applied to the side of the hood, then the pieces that covered areas that were intended to end up black were removed, leaving evenly spaced stripes covering the white that I wished to retain. While these stripes are much wider than the type you need for your locos, the technique of using the masking tape to position the striping is an easy way to keep things straight, level, and properly spaced.
The striping (and also the lettering) on the cab and tender of the loco below used dry transfers as a "mask", applied over the cab and tender, which were first painted white. Masking tape, trimmed to size, was used as spacers to keep the lettering and stripes straight and parallel, and was removed as soon as the dry transfers were applied. It's important when using this method that you do
not burnish the dry transfers as you would normally do if they were intended to remain in place. When everything was satisfactorily positioned, and the masking tape removed, the loco and tender were painted black. As soon as the paint was dry to the touch (only a few minutes, although I cleaned the airbrush before proceeding) I used bits of masking tape to "pick" at the areas where the dry transfers had been applied, removing the material, which exposed the white paint beneath.
I hope this will give you some ideas for applying striping/lining to your locos.
Wayne