Blue means one thing here: the range you are looking at.
The value chart is a row of thin gray bars, and only the selected date range fills in blue. You read the period that matters and keep the months around it as context.
The phone carries the same chart above the holdings list. Each coin gets its own small bar chart between the name and the amount, so you can scan the whole portfolio for movement without opening a single coin.
Trading screens get busy fast. This one stays light and calm, so the numbers lead: total value, realized and unrealized P&L and open positions, all on one screen.