Since my name was mentioned, yes, I have made decals for a number of reefers using my Canon BJC 2000 printer. I have created them using MSWord as well as copying them from photos on the internet and using my Camedia photo editing program. The "Premier Malt" car you see on the header was made that way. I have made white and yellow end reporting marks using white decal paper and a color background to match the car paint, but the color matching is not easy and works best for very small decals like end reporting marks.
Unfortunately, only ALPS and Kodak First Proof printers print in white. The ALPS are no longer sold, but you can find used reconditioned ones. The Kodak is too expensive for amateur use.
There are several on here that make excellent custom decals, but I'll let them come forward themselves.