Colour Variation: On-Screen Colour
The colours used within your design shown on-screen are not an accurate representation of the colours on your final printed job. The colours on a monitor are made up of red, green and blue light, while the colours on your printed job are made up of cyan, magenta, yellow and black ink, so it is not possible that they will exactly match, the colour on-screen merely provides an indication of the colours.
When designing artwork, ensure all colours are chosen from a Process / Solid to Process Pantone book to achieve a predictable result once printed. If your colours are not referenced from a Pantone Book but instead are a CMYK mix then we cannot predict how they will look when printed.