Why is the color I chose not the same as the one shown

[quan5E78]

When i choose Blue RGB(0, 0, 255) my color is changed to RGB(57, 83, 164) but other colors like red i have no problem. Can anyone help me?

[c.pfaffenbichler]

Working in CMYK can be a risk if one is not familiar with what this actually means. 

When a color is out of gamut it cannot be reproduced in the current Color Space, in this case some CMYK space you have not revealed. 

[c.pfaffenbichler]

What is the image’s Color Space (ICC Profile)?

What are the Edit > Color Settings? (Via the RGB Working Space those determine what the RGB-numbers you entered mean.) 

Please set the Status Bar to »Document Profile« and post screenshots. 

Generally speaking most commercially relevant CMYK Color Spaces are smaller than most RGB Color Spaces. 

So some colors that an RGB Color Space contains may be impossible to reproduce in a given CMYK Space. 

Edit: As an example ISO Coated v2 compared to sRGB: 

[Mylenium · Accepted solution]

There is no way to print "perfect" blue in CMYK unless you use a spot color and that is what PS is telling you by adjusting it based on your color management settings. You may want to study up on the subject.

Mylenium

[c.pfaffenbichler]

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You may want to study up on the subject.

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Maybe starting with the significance of this icon. 

https://helpx.adobe.com/photoshop/using/choosing-colors.html