Aigo RGB fans. They're from Aliexpress but they're like 50 EUR for a 5 pack of them. Cool RGB effects with a contorller for fan speed, light mode and light speed. Highly recommended with high performance
I can't recommend the Corsair ML series more highly. They are a little on the expensive side but the quality is definitely there.
At full spead (3000rpm) their at least 30% quieter than 95% of other fans, they have excellent flow with minimal cavitation and are well suited to case, Radiator or heatsink installation.