For the entire season I didn't buy red, as a mid player, because I'm bad. I thought the yellow was safer since you could bush check and, well.. wards.
I recently started playing support and now I get the red trinket every game. The disable ward aspect is just awesome, and fighting stealth champs is much easier. When ganking it's almost like a free 
passive with the vision disable.
Why am I such a noob?
10xDoublelift1 votesyou realize mid lane gets farsight (blue trinket)
top- yellow trinket jungle- red trinket( not the sweeping lense, only oracle or whatever the level 9 one is) mid-farsight so you dont have to facecheck) adc- yellow/blue (depends on how the game is going, usually blue though) support-red (get sighstone, then red trinket ASAP, then upgrade at first back once you hit level 9)
Slythion1 votesJungle/Top can both go Red/Yellow depending on the situation but ya, you're pretty much right
dakota saturn1 votesI play ap assassin mid, when I go and gank it's like I'm stealthed, making bot lane ganks a breeze, and teamfights as well.
I can imagine farsight for ADC / point and click mages like Annie so the enemy cant use a bush / fogofwar to juke you.