So in my code
let g:lightline {
/ 'colorscheme':'one dark'
/ }
Its unable to find this theme but it can find other themes without a space between the two words. I am not too sure why this is happening, how do I fix this, is there another name for this?
Just use one. When &background is dark, it switches to the dark theme of one.
Thanks for that.

It seems to work but why does it look different on my terminal? Is it cause of the terminal's configuration that has the ability to override the colors set or something?
The screen shot is taken with GUI version (16777216 colors). We can't emulate the appearance using 256 colors.
@itchyny Ah I see, so I guess I can still edit one dark theme then?
autocmd VimEnter * call s:setLightlineColors()
function s:setupLightlineColors() abort
let l:pallete = lightline#palette()
let l:pallete.normal.middle = [[ something ]]
call lightline#colorscheme()
endfunction
@itchyny THanks then.
Most helpful comment
Just use
one. When&backgroundis dark, it switches to the dark theme of one.