Lost in color space 2

AppleScript
#1

Somehow I gave up on objC and returned to plain AS and command line.

set sHtml to "<body><font color=\"#FF0000\">RED </font><font color=\"#FFFF00\">YELLOW </font><font color=\"#00FF00\">GREEN </font><font color=\"#0000FF\">BLUE </font><font color=\"#00FFFF\">CYAN </font><font color=\"#FF00FF\">PURPLE </font></body>"

set dPath to POSIX path of (path to desktop)
set htmlPath to (dPath & "tmpData.html") as string
set rtfPath to (dPath & "tmpData.rtf") as string

set shellScript to "echo " & quoted form of sHtml & " > " & quoted form of htmlPath
do shell script shellScript
--return
repeat 50 times
	set convScript to "textutil -convert rtf " & quoted form of htmlPath
	do shell script convScript
	set convScript to "textutil -convert html " & quoted form of rtfPath
	do shell script convScript
end repeat

Running the script on Mojave makes the resulting HTML useless, running it on High Sierra works fine.
Any ideas here?

#2

It’s pretty clearly a bug. But you’re probably going to have more luck finding a workaround if you explain exactly what you you are trying to do, and in what context.