The most memorable 1950s Christmas lights are bubble lights. Bubble lights were introduced post World War II and were most popular early in the decade. If you can find genuine vintage bubble lights, these will likely be the most ooh’d and ahh’d over. Remember that these lights are very hot and you should place them carefully, even on artificial trees. You might place your precious strings on a plug connected to a light dimmer switch and reduce the amount of power just enough to keep them bubbling, thereby increasing the life of the bulbs and not reducing the brightness of your tree very much. These bulbs are very difficult to pry apart and replace with a modern replacement bulb and working vintage ones are increasing in price as they become scarcer. If you want the look without the wear to your precious vintage lights, invest in some reproduction bubble lights for your tree and save your vintage set for a special place on a wreath or garland and light them less frequently than you do your tree.
The predominant lighting sets were C9 and C7 sets. A bit harder to find are G7 sets with a globular shaped bulb. The 50s saw the decline of the C6 or Mazda light sets, though they were still manufactured during the 1950s. Specialty figural light bulb sets saw their end in the 1950s. Very few were produced early in the decade. If you use any of these light sets on your tree, you are being authentic.
In 1958, the very first aluminum trees were produced and with the fire hazard of placing light strings on aluminum branches, the color wheel was born. These rotating flood lights lit up the whole tree in 4 different primary colors.