The Color panel is used to choose color for various brush tools and to apply color to the stroke and fill of vector shapes, lines, and text.
About the Color panel
The Color panel can operate in several color modes—RGB, RGB Hex, HSL, CMYK, LAB and Grayscale—and has various ways of presenting color options—using sliders, a color wheel (HSL only), or color boxes. Color tints can also be applied from within the panel.
Color panel (RGB sliders): (A) Primary/Secondary color selectors with color 'none' swatch and 'swap' arrow, (B) RGB sliders, (C) RGB spectrum, (D) Opacity/Noise/Intensity toggle, (E) Panel Preferences, (F) Color model selection, (G) Color picker tool and picked color swatch, (H) Opacity control, (I) Noise control, (J) Intensity control (32 bit documents only).
The active color selector is shown at the front of the two color selectors. Choosing a new color will apply it to the active color selector.
For vector shapes, lines and text, the color selector is for stroke and fill color instead of Primary and Secondary color, respectively.
Using the Color panel
With the Color panel, colors can be set for use by a tool in just a few clicks. Opacity and noise are further color attributes which can be applied via slider. Additionally, for 32-bit unbounded HDR documents, an intensity attribute is available as a slider for creating unbounded color values.
To set the color of a selector:
Click the selector you want to apply the color to. It will show at the front of the two color selectors.
Do one of the following:
Choose a color from the color model's Sliders, Wheel (HSL only), or Boxes.
Click the picked color swatch.
Click the None swatch to make the color completely transparent (for the tool, fill or stroke).
To switch colors between the selectors:
Click the double-headed arrow. The colors switch but the active swatch selector remains the same.
To adjust opacity, noise or intensity setting:
Select the Opacity/Noise/Intensity toggle button on the bottom-left of the panel.
Drag the slider to set the value.
Color selection preferences and color models
When choosing colors in the Color panel, you can choose from various selection preferences and color model values. The color selection preferences are changed in the Panel Preferences menu.
Depending on the color model selected, you can also choose to work in 8 bit, 16 bit or Percentage mode.
Some of the selection methods allow you to set color using values other than RGB. This doesn't change the working color profile of the document, but changes the input values for the colors.
The following color selection preferences are available from the Panel Preferences menu.
Wheel—HSL Color Wheel
Drag on the outer ring to set the hue.
Drag in the triangle to set saturation and lightness.
Sliders—RGB, HSL, CMYK, LAB, Grayscale
Select the color mode from the pop-up menu.
(Optional) From the Panel Preferences menu, select 8 bit, 16 bit or Percentage.
Drag sliders or type directly into the value boxes to set the color values.
Boxes—Hue, Saturation, Lightness only
Hue—Drag on the hue slider to set the hue, drag in the box to set the saturation and lightness.
Saturation—Drag on the saturation slider to set the saturation, drag in the box to set the hue and lightness.
Lightness—Drag on the lightness slider to set the lightness, drag in the box to set the saturation and hue.
Tint
Drag the slider to the left or right to increase or decrease the color tint, respectively.
For any selected object, the Color panel will remember the color mode that the object was created in. Instead, using Sliders you can lock the color mode (e.g., CMYK sliders) to prevent the mode from changing. This avoids inadvertently swapping to another mode after using swatches or selecting a different object created with a different color mode. This lock only works on the current session; subsequent sessions will use the HSL color wheel as default.
Using the Color Picker
The picker lets you sample colors within or outside Affinity Photo, then use them in your design.
To use the Color Picker:
Drag the Color Picker icon to the color you want to sample.
Click the selector in the Color or Swatches panel you want to apply the color to.
Click the swatch next to the Color Picker to apply the color.
Saving chosen colors for later use
Once your color has been chosen and applied to a tool or content, there are several ways to preserve this color for later use.
The following options are available from the Panel Preferences menu.
Copy Color to Clipboard as Hex—this calculates the current color's Hex value and adds it to the clipboard. This is useful for web developers, to standardize on colors between graphics and HTML coding in a web environment.
Add Color to Swatch—adds the current color to the currently loaded palette in the Swatches panel.
Add Chord to Swatch pop-up menu—adds a chord of the current color to the currently loaded palette in the Swatches panel.
When choosing colors in the Color panel, you can choose from various selection preferences and color model values. The color selection preferences are changed in the Panel Preferences menu.
For any selected object, the Color panel will remember the color mode that the object was created in. Instead, using 
To use the Color Picker: