Firstly calibrate your monitor. Then in Photoshop:
- Go to Edit > Color Settings and set the working space for RGB to Monitor RGB.
- Open a document then Edit > Assign Profile, then set it to Working RGB. This has to be done for every document you work on.
- Make sure View > Proof Colours is turned off.
- When saving files use Save for Web & Devices, ensure that Convert to sRGB is turned off. If you’re saving a JPEG file, then also turn off Embed Color Profile.
And that’s it.