There are two types of LEDs that can be sewn, the simple led (light emitting diode) that we all know and the led created by Lilypad, the latter are ready to sew and resist washing, which are normally used in textile projects.


To sew Lilypad leds you simply have to introduce the needle with conductive thread, they have the + and - symbol on each side, they are very easy to work with and come with built-in resistance.
To sew normal leds there is a trick to differentiate the pins, the longest is the + and the shortest is the -.
If before sewing we bend them with different shapes we will know which corresponds to - and +.

These LEDs do need resistance if you do not want them to burn, it is not convenient to wet them and if you do, make sure they are very dry before turning on the circuit.
Depending on the color they need more or less power, I recommend that you measure the voltage of each LED to see its consumption, it may happen that you mix colors and some do not light up.