Let’s get technical, the terms warm white and cool white refer to the high and low end of the white light colour spectrum.
Warm white casts a yellow hue and is most often used in the home it’s a comforting, tranquil and welcoming light. Use on a green tree with traditional Christmas colours like red, green and gold. Also a popular choice for decorating the Christmas table, warm white adds a cosy glow more like that of a traditional wax candle flame.
In contrast cool white leaves a blue hue and adds a bright, fresh and clinical glow. Most effective for outdoor decorating. Cool white goes well with shades of blue, grey and silver it looks terrific on a white tree and adds a brilliance that’s hard to match.
Remember there are no rules. Lately it’s become very popular to see warm white lights in a flocked or white tree a look I particularly like. An instant update if your tired of the same style year after year but want to keep the same Christmas tree.