Conversion is from 24 bit RGB of this theme into the 256 color Xterm palette. The naive conversion script obtains e.g. "#d7afaf" as argument and its source-code is:

fromhex () {
	local hex r g b
	hex=${${1#"#"}#0x}
	r="0x${hex[1,2]:-0}"
	g="0x${hex[3,4]:-0}"
	b="0x${hex[5,6]:-0}"
	printf -- '%03d\n' "$(( (r<75?0:(r-35)/40)*6*6 +
                        (g<75?0:(g-35)/40)*6 +
                        (b<75?0:(b-35)/40) + 16 ))" | tee >(pbcopy)
}