If there are multiple lines in the same line charts, the colors are not a good way to distinguish the different lines. Sometimes the lines may be overlapping and it might be hard to see what line is which one since the mouse focus point is jumping if lines are close each others. In these kind of cases the color picker does not bring any value.
Please consider implement a way to change or remove the line color picker from line chart legend and replace it with a possibility of clicking the line which would toggle the line visibility on and off.
Please consider implement a re-scaling of y-axis if one line visibility is toggled on or off. For example if one line is 100 in y axis and rest 5 lines are between values 1-5, the chart should re-scale to allow viewing the lines with much smaller values.