Only script install avaible. Download installer first:
git clone https://github.com/SLywnow/hi-themes-refind
And then run installation script:
sudo ./hi-themes-refind/setup.sh -rEFInd_directory-
For example:
sudo ./hi-themes-refind/setup.sh /boot/efi/EFI/rEFInd/
You can make your own theme, or use preset;
Dark Preset Light Preset Red Preset Green Preset Blue Preset Purple Preset