What does the colored Circles or Cubes around the news paper corner symbolises?

Question

I have observed different news papers corners are with few colored circles or cubes. Usually the colors are Blue, Pink, Yellow and Black. May I know what its symbolises? Is there a meaning for these colors?

Answer 1

What he said

Answer 2

used for print press to proof match correct colours and alignment,

http://printingupdate.com/content/view/2...

http://www.rti-rips.com/HeidelbergDIRIPK...

heidelberg print press,

http://www.heidelberg.com/www/html/de/co...

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