What is the last Super Saiyan version Goku can reach currently? I've recently had a strong argument with my friends about the last version of Super Saiyan Goku can transform into, but we argued that the last super Saiyan is Super Saiyan God and one of my friends mention like Super Saiyan Rose. Now in our defense we haven't watched a lot of the DBZ series of late, but does this SS Rose even exist and what are the powers or features of the character at that phase? thanks.
Super Saiyan Rosé is a transformation achieved by Black Goku (who is an evil kaioshin from another universe who stole Goku's body from another timeline)

Super Saiyan Rosé

The last transformation Goku can achieve is either Super Saiyan Blue (also called super saiyan god super saiyan) or Ultra Instinct , depending if you consider Ultra Instinct a transformation or a state (because Ultra Instict can be achieved by non saiyans too). In Ultra Instinct Goku has a white aura, black hair and grey eyes.

The transformation called super saiyan god, where Goku has red hair and red eyes isnt the last transformation of Goku. 

Super Saiyan Blue (also known as Super Saiyan God Super Saiyan)

Ultra Instinct

Super Saiyan God