ios - xcode slider value to change background color -

ios - xcode slider value to change background color -

hey making simple slider app utilize slider in xcode 4.6 ios app 1 in illustration http://www.mobisoftinfotech.com/blog/iphone/iphone-slider-control-uislider-control-tutorial/

but set reading 7.0-9.0 , cant find how create alter background color slider moves. "red" if out of tolerance "yellow" if close , 'green' if on money :) maybe switch statement ?? totally new , trying larn give thanks help guys , girls

ios objective-c xcode