Hi, 
In kendo Line chart, currently the plot area can be colored using plotBands. 
In line with that is the requirement to color different ranges with different colors in the y-Axis line alone.
The line size can be made to 3 or 5 px to shown the color clearly.
This will help the user 
1. to understand the criticality of the different ranges.
2. Mostly line charts will be shown shown in reports, and will be given as printouts to the patients (in case of hospitals),  a report will have multiple line charts components, providing this feature will help the customers to reduce the cost on printer color catridges (that will be used when printing the whole plotbands for different ranges).

Thanks.