I want to use the same components used in the images below but I can't figure out if they are third-party components or just modified ones because I tried to modify the theme but could not get the same results. (I am on Embarcadero Delphi 11.3)
1- This Page Control (it has a custom Color)
2- This Button


I don't know how to answer that for the PageControl. Try using a tool like Spy++ or WinSight to look at the UI's elements and see what their actual class names are, that might give you a clue to whether it is a standard control or a custom control.
The buttons look like the standard Win32 Command Link control. The VCL's standard
TButtoncomponent supports that type via itsStyleproperty, which you can set tobsCommandLink. The 1st line of text is set by the button'sCaptionproperty, the 2nd line of text is set by theCommandLinkHintproperty, and the image is set by theImagesandImageIndexproperties.