my fav btop theme

sudo apt install -y btop
wget https://github.com/catppuccin/btop/releases/download/1.0.0/themes.tar.gz
tar xzf themes.tar.gz
rm -rf themes.tar.gz
mkdir -p ~/.config/btop
cd .config/btop/
rm -rf themes/
mv ~/themes .
cd ~

run btop and then press ESC - select option and then your preferred theme.

or

vi .config/btop/btop.conf 
color_theme = "~.config/btop/themes/catppuccin_macchiato.theme"