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In over–simplified terms:
Each individual monitor profile has TWO PARTS:

• Part One is used ONLY by the Operating System (OS) and non–color–managed applications.

• Part One tells the monitor how to display the colour.

• Part Two is used ONLY by color–managed applications (like Photoshop).

• Part Two tells the Color Management System how the monitor displays color.

This explains HOW Photoshop, a color-managed application, can display bad color when the color looks good in other applications like Microsoft Word, FireFox:

• The part of the monitor profile Photoshop uses is bad.

• The part the OS and non–color–managed applications use is still good.

An EASY WAY TO RULE OUT A BAD MONITOR PROFILE is to set the profile display properties to a fresh, generic sRGB profile. On a Mac OSx, go to System Preferences> Displays> Color and highlight sRGB IEC61966-2.1 (or sRGB), then reboot and test for color issues.

Don't be mislead on this point — many users have reported defective hardware "pucks" that build defective profiles and certain monitors won't display properly through custom ICC profiles — so try setting sRGB before giving up to confusion.

If the symptom is an intense color saturation shift (especially in the reds), you are probabably on a Mac and using a wide-gamut monitor.

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BROKEN COLOR MANAGEMENT is the number two SUSPECT:

How to FIX Photoshop color management:
See my: Set Up Photoshop Color Management

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Photoshop is a color–managed application.
See my: Basic Theory Behind Photoshop Color management

As a color–managed application:
Photoshop's Color Management System Converts a file's Source Space into MonitorRGB (the monitor's "calibrated" colorspace) and thereby displays the tagged file's "true color" through the monitor's "calibrated" colorspace.

• Non–color–managed applications do not "see" the embedded tag.

• Non–color–managed applications do not Convert any color based on the embedded tag.

Thus, non–color–managed applications will display a file differently than Photoshop (unless the file was last Saved in the viewing monitor's specific colorspace).

See embedded ICC Profiles in action Color Management tutorial
Includes Tagged and UnTagged sRGB, AdobeRGB, AppleRGB
Monitor calibrating and profiling tips, 2.2 gamma, 1.8 Mac gamma, D65 6500 Kelvin.

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IF PHOTOSHOP IS DISPLAYING A GOOD FILE BAD (or if it has spoiled color pallets) — the monitor profile is bad, or we've broken Photoshop's color management system settings, or the install is corrupted, or the hardware is bad....

See Adobe Photoshop Assign Profile and Convert to Profile tutorial
Includes Photoshop downloads .jpg .tif .png .gif files of Tagged and Un Tagged sRGB, Adobe RGB (1998), Apple RGB and written basic information to understand how Adobe Photoshop handles color profiles.