Buffer 0 appears to be the Close price of the blue candles and Close price of the red candles. Otherwise its value is 0
... and so on...
Get some Trace block, play with it in Visual mode and you will eventually understand what each buffer means. Then how to use them... I don't exactly know. Even the built-in Heiken Ashi is kinda weird. I used to detect red/white candle by comparing the values from 2 of the buffers.