The above image is a Windows 95 default background. I wanted to know how they achieved this effect and was wondering if it is possible in Photoshop or if I need a dot-matrix printer or maybe a graphic-design program from the 90’s to replicate it.
Answer
Open a photograph in Photoshop
Do Image > Adjusments > Desaturate
Then Image > Mode > Indexed color, and use the settings shown below.
Note: Afterwards, you can switch back to other modes such as RGB for further editing, by using Image > Mode > RGB
Attribution
Source : Link , Question Author : jomo , Answer Author : Billy Kerr