is it possible to change the RSI 30/70 range and color

There may be different options on the Pro level subscription so I can't speak on that. On the Extra level, on SharpCharts, one way would be to use the Annotation tools and add a color filled rectangle with low opacity over the areas of the chart you'd like colored. This would only work on a chart by chart basis.

Another way, although not as optimal as the annotation, is to use Horizontal Line overlays on the RSI.

https://support.stockcharts.com/doku.php?id=sharpcharts:reference

You can color the horizontal lines how you'd like.
So a Horizontal Line parameter of

5:red,10:red,15:red,20:red,25:red,30:red

would put a series of lines between 5 and 30 on the RSI panel.

adding the green lines to the parameter box

70:green,75:green,80:green,85:green,90:green,95:green

would color between 70-95 with green lines.

5:red,10:red,15:red,20:red,25:red,30:red,70:green,75:green,80:green,85:green,90:green,95:green



You can adjust the lines closer or further apart to fit your eye.

below is the Line option with the parameters I showed above and the Annotation method below.