Like the other guy said, the appearance of the actual terminal is determined by the profile, and the applied color scheme.

The color scheme of Konsole is part of the profile. To create a new one: Right click anywhere>Menu>Settings>Configure Konsole

Click profiles, in the top right click “New”.

Click Appearance. From here you can add, change, and edit the available color schemes. Once you’re happy, click Apply. Close the dialogue.

Select the new profile and make it the default. Done.