The DTP world is essentially a world at 4 colour… plus spots here and there.
Spot Colour: Spot colours are those which are obtained with a specially mixed ink, instead of being formed by CMYK colours. Through the use of spot colours you can achieve consistency throughout publications linked by the same branding, or use colours which are not achievable by using the CMYK method, such as a metallic silver colour.
Spot colours can be used to also create pubblications which only use 2 or 3 colours thus resulting in money savings. The most used matching system for spot colours is Pantone’s, though there are many others.


I wish to know how can be Pantone shade ref.no.can be determined from CMYK?
For example: c=0,m=0,y=0 k=65 or
c=0,m=100,y=50,k=55
Thanks,
Girish
I am not sure I understand well your question, but if you want to know how to match a PANTONE colour by using CMYK colours you either need to use a PANTONE Swatch book or you can have your DTP application do it for you.
For example, if you chose a PANTONE colour in InDesign or QuarkXPress, you can tell either program to change the property of the colour from spot to process. InDesign and QuarkXPress will output the Pantone colour as a mix of CMYK colours.
Beware that not all PANTONE colours can be reproduced as CMYK colours. You can read this article for more information: The Pantone Matching System: Always Show Your True Colours.
The PANTONE guide you want to use to match PANTONE colours to their CMYK equivalent is called PANTONE Bridge. If you want to see it, click here.
what is the pantone bridge? I work with indesign and am having trouble getting pantone colors with cymk for advertising in magazines.Do i have to buy the pantone bridge to work with indesing in order to get the right colors?