it is unofficial repository maintained by me @hax4us. you can check available packages in README
wget https://github.com/Hax4us/TermuxBlack/raw/master/install.sh
bash install.sh
apt install pkg_name
rm -f $PREFIX/etc/apt/sources.list.d/termuxblack.list && mv $PREFIX/etc/bash.bashrc.bk $PREFIX/etc/bash.bashrc && rm -f ~/.termux/colors.properties