Following is the solution to remove gray color
border of UITextField
.
Problem

Solution

For that you need to use following one line of code Just change the border style
_firstName.borderStyle = UITextBorderStyleNone;
CAShapeLayer *border = [CAShapeLayer layer];
border.strokeColor = [UIColor gray].CGColor;
border.fillColor = nil;
border.lineDashPattern = @[@4, @2];
border.path = [UIBezierPath bezierPathWithRect:_firstName.bounds].CGPath;
border.frame = _firstName.bounds;
[_firstName.layer addSublayer:border];
_firstName.borderStyle = UITextBorderStyleNone;
UPDATE
For Rounded corner use following function.
- (void)drawDashedBorderAroundView:(UIView *)v
{
//border definitions
CGFloat cornerRadius = 10;
CGFloat borderWidth = 2;
NSInteger dashPattern1 = 8;
NSInteger dashPattern2 = 8;
UIColor *lineColor = [UIColor orangeColor];
//drawing
CGRect frame = v.bounds;
CAShapeLayer *_shapeLayer = [CAShapeLayer layer];
//creating a path
CGMutablePathRef path = CGPathCreateMutable();
//drawing a border around a view
CGPathMoveToPoint(path, NULL, 0, frame.size.height - cornerRadius);
CGPathAddLineToPoint(path, NULL, 0, cornerRadius);
CGPathAddArc(path, NULL, cornerRadius, cornerRadius, cornerRadius, M_PI, -M_PI_2, NO);
CGPathAddLineToPoint(path, NULL, frame.size.width - cornerRadius, 0);
CGPathAddArc(path, NULL, frame.size.width - cornerRadius, cornerRadius, cornerRadius, -M_PI_2, 0, NO);
CGPathAddLineToPoint(path, NULL, frame.size.width, frame.size.height - cornerRadius);
CGPathAddArc(path, NULL, frame.size.width - cornerRadius, frame.size.height - cornerRadius, cornerRadius, 0, M_PI_2, NO);
CGPathAddLineToPoint(path, NULL, cornerRadius, frame.size.height);
CGPathAddArc(path, NULL, cornerRadius, frame.size.height - cornerRadius, cornerRadius, M_PI_2, M_PI, NO);
//path is set as the _shapeLayer object's path
_shapeLayer.path = path;
CGPathRelease(path);
_shapeLayer.backgroundColor = [[UIColor clearColor] CGColor];
_shapeLayer.frame = frame;
_shapeLayer.masksToBounds = NO;
[_shapeLayer setValue:[NSNumber numberWithBool:NO] forKey:@"isCircle"];
_shapeLayer.fillColor = [[UIColor clearColor] CGColor];
_shapeLayer.strokeColor = [lineColor CGColor];
_shapeLayer.lineWidth = borderWidth;
_shapeLayer.lineDashPattern = [NSArray arrayWithObjects:[NSNumber numberWithInt:dashPattern1], [NSNumber numberWithInt:dashPattern2], nil];
_shapeLayer.lineCap = kCALineCapRound;
//_shapeLayer is added as a sublayer of the view, the border is visible
[v.layer addSublayer:_shapeLayer];
v.layer.cornerRadius = cornerRadius;
}
Call this function using below code.
_firstName.borderStyle = UITextBorderStyleNone;
[self drawDashedBorderAroundView:_firstName];
May this help lot.