The Riso machines don’t really know what “colour” your artwork is. They read each file as information about where ink should be printed and how densely it should be printed. Think of each colour in your artwork as a separate greyscale layer.
So, if you want to print a yellow circle, you don't make the circle yellow in your supplied file. You supply it as black or greyscale and tell us that the layer is to be printed in yellow.
Digital Artwork Artwork_Horse_Blue.PDFArtwork_Horse_Red.PDFArtwork_Horse_Yellow.PDF Artist: Malika Illustration Printed by: Dizzy Ink Artwork_Horse_Blue.PDFArtwork_Horse_Yellow.PDFArtwork_Horse_Red.PDFIf you're supplying a colour-separated file yourself, make sure each separation is clearly named with the ink colour you want it printed in.
For example
Poster_pink.pdf
Poster_aqua.pdf
Poster_black.pdf
Clear files make everyone's life easier and reduce the chance of the wrong colour being assigned to a layer.