How change a CGContext attribute after drawRect is carried out

I draw a path using CGContext.

How can I later change one of the path attributes aft开发者_运维知识库er drawRect was carried out (completed)? I want to be able to change the color of my path according to a slider value.

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defined the property and added [setNeedsDisplay] during property change did the deed ...

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To set color use this function

CGContextSetRGBFillColor(context, RED, GREEN, BLUE, ALPHA);

where RED, GREEN, BLUE, ALPHA, stands for float values from 0 to 1