@bakman2 Thank-you! That worked. 
I found an alternate method for a node before the HSV>RGB node. That consists of -
msg.payload = msg.payload.replace("hsv(", "").replace(")", "").split(",");
return msg;
The output format is now [ "359", "69", "100" ]. That is accepted by the HSV>RGB node.
Your function after the colour convert node filled the missing link!
I've spent days getting nowhere trying to learn this new discipline...it looks so simple afterwards. 