Reactive Cocoa. Don't you just got to love it?

gistfile1.m

    NSArray *items = @[_gainSlider, _frequencySaturation, _driveSlider];
    NSArray *signals = [[[items rac_sequence] map:^id(id value) {
        return [value rac_highlightSignal];
    }] array];
    
    __block BOOL triggering = NO;
    [[RACSignal merge:signals]
        subscribeNext:^(RACTuple* value) {
            if(triggering) { return; }
            triggering = YES;
            for(id item in items) {
                if(item != value.first) {
                    [item setHighlighted:NO];
                }
            }
            triggering = NO;
        }];
    
    FlatMapping color = ^RACStream *(RACTuple *value) {
        NSColor *color = [value.second boolValue] ? almostWhite : unhighlight;
        return [RACSignal return:color];
    };

    RAC(self.driveLabel, textColor) = [[_driveSlider rac_highlightSignal] flattenMap:color];
    RAC(self.driveValue, textColor) = [[_driveSlider rac_highlightSignal] flattenMap:color];
    RAC(self.gainLabel, textColor) = [[_gainSlider rac_highlightSignal] flattenMap:color];
    RAC(self.gainValue, textColor) = [[_gainSlider rac_highlightSignal] flattenMap:color];
    RAC(self.saturationLabel, textColor) = [[_frequencySaturation rac_highlightSignal] flattenMap:color];
    
    [[[_driveSlider rac_valueSignal] map:^id(id value) {
        return [NSString stringWithFormat:@"%.1f", [value doubleValue]];
    }] subscribeNext:^(id value) {
        [self.driveValue setStringValue:value];
    }];
    [[[_gainSlider rac_valueSignal] map:^id(id value) {
        return [NSString stringWithFormat:@"%.1f", [value doubleValue]];
    }] subscribeNext:^(id value) {
        [self.gainValue setStringValue:value];
    }];