Which cube should I add next?

Speedrun

I found a secret one

Hints I Can Find : Brown : Mix Red And Green Blue : Touch The Water White : Touch The Sky Purple : Touch The Spikes Lime : Mix White And Green Pink : Mix Red And White Light Brown : Mix Brown And White Cyan : Mix Blue And White Yellow : Touch The Banana Orange : Mix Red And Yellow Cream : Mix Yellow And White Black : Throw White In The Water Long Green : Touch The Green Thing

18/22

Yeah black + white is vanilla