Highchart won't show all the stocks in different color

I just finished my (StockChartApp)[https://yasser-chartstocks.herokuapp.com/].

But HighChart is behaving weirdly.

When I add a new stock, the stock gets updated but it gets the color of a previous stock.

But when I refresh all stocks have different colors.

Any guesses why that could be happening ?

Here is the relevant HighChart code