While the lightsaber is an iconic aspect of Star Wars' era-spanning conflict between the Jedi and the Sith, it means something very different to the dark side's adherents than to the Jedi Order. While the Jedi consider lightsabers an expression of skill and focus - an "elegant weapon for a more civilized age" - the Sith regard them with far less respect.
Sith lightsabers are red because the Kyber crystals that give them their power have been corrupted, tortured until they 'bleed' in order to better access the dark side. This gives the very act of possessing a red lightsaber an intimidating psychological advantage, as it speaks to the horrifying process that created it and immense pride in one's commitment to the dark side. However, this also means that red lightsabers very obviously indicate dark side allegiance and usually the Sith faith. It's partly for this reason that Emperor Palpatine rarely used his own dual blades, as they would have exposed his true nature while plotting against the Jedi.
In Star Wars #25's 'The Lesson' (from Charles Soule, Giuseppe Camuncoli, Daniele Orlandini, Arif Prianto, and Clayton Cowles) Palpatine trains Darth Vader on Coruscant, commanding him to fight for his life. Vader does so, crossing blades with Darth Sidious in an epic duel, but is quickly downed as his master uses the Force to batter him with detritus. Palpatine mocks Vader for thinking of his lightsaber as his main weapon - and even for thinking of it as a weapon at all. Darth Sidious insists, "The saber is merely a symbol. A flame, signifying the great blaze of the dark side. The inferno that consumes all who come against it."
According to Emperor Palpatine, the lightsaber is little more than a symbolic tool used to express allegiance to the dark side. In the Legends-era novel Dark Lord: The Rise of Darth Vader (by James Luceno), Palpatine goes further, saying that the Sith have outgrown lightsabers and only continue to use them in order to scare and humiliate the Jedi, especially in those cases where they seize and corrupt Jedi weapons (as Darth Vader did to claim his own Sith lightsaber.)
Palpatine's belief about the real meaning of lightsabers to the Sith is a twisted reimagining of Jedi ethos, but one that holds true to how he fought his battles in Star Wars lore. At least by the time of the original Star Wars trilogy, the Sith treated lightsabers as incidental weapons whose primary function was to pervert and mock the Jedi way, while also working as an effective way to kill their lessers that still paled in power to the Force.