This is a version of https://github.com/altercation/vim-colors-solarized modified to always use true color (24 bit rgb). This means it will work with neovim-qt with the following:

In file ~/.config/nvim/ginit.vim :

let $NVIM_TUI_ENABLE_TRUE_COLOR=1
set background=light " or dark
colorscheme solarized_nvimqt

For Neovim terminal version, in file ~/.config/nvim/init.vim, keep :

set background=light " or dark
colorscheme solarized

For more info see the original.