How To Make Rainbow Colors In Affinity Photo For Beginners
Create something for the preset, such as rectangle via the rectangle tool but equally it could be an ellipse or design created with the pen tool. Go to the gradient tool and go to the editor at the top left of the control bar. Apply your preset from left to right and hold down the shift key to create it in a straight line
In the editor panel, you will probably see two initial stops as the far ends. Click the insert button to add a 20% and click again to add a 40% and 60% and 80% stop, you will need to set the position entry manually.
Set the colors
Set to RGB sliders. Click on the color entry Set the first stop to 255, 0, 0 for red; 255,255, 0 for yellow for the second, 0,255,0 for green, 0,255,255 for light blue; 0,0,255 for darker blue 255,0,255 for purple.
Go to the move tool and select the rectangle with the colors
View menu and studio. Go to the category you want to store your preset in and click the little + button beside the category to add this preset to the panel for future use. You can then select a shape etc and then use the tool and select the preset from the swatches and use the tool to change it from linear to radial etc as well as position the origin and change the length and angle.
You can now use the tool to apply it. You can only apply it once to the shape but if you want to combine it with other layers, perhaps use the fill layers via the layer menu instead.
You can fill a shape or use a brush stroke / layer filled with a gradient and then use the motion blur effect to blur it at an angle and then use multiple copies of it via alt / option and distort the layers
Fills / strokes
You can use it applied to all kinds of designs, use it as a fill for a shape as well as use it as a stroke and that can be applied via the tool and selecting the presets from the swatches panel. With the tool selected, drag in linear style or radial etc and apply this colorful design to a stroke (or fill). You can then modify the length and angle of the effect. If you applying to something like a dumbbell shape then you may wish to hold down the shift key and drag across the design and the stroke will be applied. You can then apply layer styles etc and that also can use the same colorful preset via the overlay.