When you toggle the layout on PC, the buttons at the bottom of each post (i.e. quote, hugs, etc...) will change colour and shape, as well as colour changes to the entire site. Check at the bottom left, the normal is, "PsychCentral", although "Default" has a similar colour layout. If it is set to PsychCentral, then your screen resolution is different on your new comp.

If you want to change it, right-click on your desktop -> Screen resolution -> Advanced settings -> Monitor. If the screen is brighter than what you prefer, click the battery icon at the bottom-right of your screen, click adjust brightness then toggle the brightness scale (or input a value if it allows).