DST and EXP are formats that don't have colors, they have color stops. A design in a file looks awful. The digitizer puts in the colors they want.
Here's a Converter:
http://www.wilcom.com/en-us/products/truesizer.aspx
Another one:
http://oesdartsizer.com/
They will save in PES.
They both will show the picture of the file. Make sure that it isn't just red, blue, green, black, etc where the color stops are located and actually has the colors. I use Designers Studio, and it will show all the formats.