@king, it is explained in the manual under the "Bid/ask trend indicator" section.
Thanks for the reply. Yes I read that. It only explained the "Bid/ask trend" column. I was asking about the "Last" column as below which is colored by both green and red in varying ratio.
@king, I apologize. I misunderstood the question.
I hope someone else or @Tomasz will be able to provide you the correct answer.
Colors used are typical: GREEN when price changed up, RED when price changed down. Black if it did not change from recent update.
The background shows where current price is within current day's High-Low range. If green bar is near the left side (so green is thin and red spans majority of area) it means current Last price is near Low. If green area is wide it means that current Last price is near High.