动画时如何更改CALayer的颜色

Question

I have an arc that goes around in a circle and changes colors three times. I used an example on SO to get me started: Change CALayer color while animating

This example works, however the colors are red, then green then blue. I would like them to be Green, Orange, then Red. I'm trying to figure out how in the code he changed colors, and it's quite confusing to me:

for (NSUInteger i = 0; i < 3; i++)
        {
            CAShapeLayer* strokePart = [[CAShapeLayer alloc] init];
            strokePart.fillColor = [[UIColor clearColor] CGColor];
            strokePart.frame = tutorialCircle.bounds;
            strokePart.path = tutorialCircle.path;
            strokePart.lineCap = tutorialCircle.lineCap;
            strokePart.lineWidth = tutorialCircle.lineWidth;

            // These could come from an array or whatever, this is just easy...
            strokePart.strokeColor = [[UIColor colorWithHue: i * portion saturation:1 brightness:1 alpha:1] CGColor];

So I believe this line is doing the color change:

strokePart.strokeColor = [[UIColor colorWithHue: i * portion saturation:1 brightness:1 alpha:1] CGColor];

My goal is to manipulate those colors to Green Orange Red instead of Red Green and Blue.

Thanks

EDIT:

This is the value of portion:

const double portion = 1.0 / ((double)3);

Answer 1

The HUE-Color system defines the color in a an angle of 360 degrees, where 0 is red, 108 (360*0,3) is a green and is a blue. This is how the colors get generated:

strokePart.strokeColor = [[UIColor colorWithHue: 0 saturation:1 brightness:1 alpha:1] CGColor]; // RED

strokePart.strokeColor = [[UIColor colorWithHue: 0.3 saturation:1 brightness:1 alpha:1] CGColor]; // GREEN

strokePart.strokeColor = [[UIColor colorWithHue: 0.6 saturation:1 brightness:1 alpha:1] CGColor]; // BLUE

If you want to change to colors, you could shift the portion by some other value:

strokePart.strokeColor = [[UIColor colorWithHue: 0.3 + portion saturation:1 brightness:1 alpha:1] CGColor];

Or you could define yourself an array, with your colors you want to go through:

NSArray* colors = @[ UIColor.green, UIColor.orange, UIColor.red ];
for (id color in colors)
    {
        CAShapeLayer* strokePart = [[CAShapeLayer alloc] init];
        strokePart.fillColor = [[UIColor clearColor] CGColor];
        strokePart.frame = tutorialCircle.bounds;
        strokePart.path = tutorialCircle.path;
        strokePart.lineCap = tutorialCircle.lineCap;
        strokePart.lineWidth = tutorialCircle.lineWidth;

        // These could come from an array or whatever, this is just easy...
        strokePart.strokeColor = [color CGColor];

Answer 2

Ah I just figured it out. Here is the answer below:

if (i == 0) {
               strokePart.strokeColor = [UIColor greenColor].CGColor;
            }

            else if (i == 1) {
                strokePart.strokeColor = [UIColor orangeColor].CGColor;
            }

            else if (i == 2) {
                strokePart.strokeColor = [UIColor redColor].CGColor;
            }