Unfortunately it is not possible to change the wick/shadow color of a candlestick.
To configure chart color settings:
- Click on the Configure wrench icon in the top-right of the chart
- Select Configure Font followed by Chart Colors on the left side. This will show you all of the options to change chart colors, but candle shadow color is not an option.
For more information on how to change chart colors, see the TWS Users' Guide.