Lanyards come in a wide variety, and what is best depends on what you want. If it is functional, you barely need anything (a loop and a diamond knot), but a cosmetic improvement will be personal preference.

I suppose the specific type depends on what you are going for. Are you going to use it in water? Dirt? With gloves? In extreme conditions? What type of knife is it? How much force do you need to apply? Will the lanyard have another function?

Small lengths of paracord are usually grossly overpriced. Also, it can be difficult to work with short lengths. It is better to get long pieces and then do what you want, and trim as needed.

Also what is your all time favourite colour, pattern and knot style ?

I never actually carried a knife with a lanyard for any length of time, but I like solid colours (black, usually) and a snake knot with a simple diamond knot to hold it all together.