Design of the application
The app PDF4Teachers is using the JavaFX theme JMetro, which is imitating the Windows 10 theme.
Logo of PDF4Teachers
Keys colors
Base Gradient
#EC247F → #EE3225
Dark Gradient
#7D1343 → #7E1A13
Dark Red
#840C2C
Dark Blue
#3C3B4B
Purple
#8C8AFF
Gray
#D0D8EB
Images and screenshots
Figma
Many of PDF4Teachers' designs are available on Figma. There, you will be able to export anything, in the size you want.