Adjust the tonality of your composite with Curves

Long press the plus icon from the taskbar to bring up more add layer options — New layer, Adjustment layer, New empty group, and Paste as new layer. Select Adjustment layer.

Under Adjustments, you can select any of the adjustment options — Brightness/Contrast, Black and white, Color balance, Curves, Exposure, Hue/Saturation, Levels, and Vibrance.

Choose Curves to apply curves adjustments. 

Under Curves in the Layer Properties panel, tap anywhere on the straight diagonal line in the histogram to add nodes. As you add nodes to the diagonal line and move them, the shape of the curve changes, reflecting your adjustments. The steeper sections of the curve represent areas of higher contrast while flatter sections represent areas of lower contrast. 

• Moving a node in the top portion of the curve adjusts the highlights. Moving a node in the center of the curve adjusts the midtones, and moving a node in the bottom section of the curve adjusts the shadows.
• To darken highlights, move a node near the top of the curve downward. To lighten the shadows, move a node near the bottom of the curve upward.
• Moving a node either down or toward the right maps the Input value to a lower Output value, and your composite darkens. Moving a node either up or to the left maps a lower Input value to a higher Output value, and the composite lightens.

Instead of adding a node, you can also manually enter an Input value and required Output value to apply a specific adjustment to your photoshop document.

Tap the bin icon to delete a node.

Note: In Photoshop desktop, you can simply drag a node to the edge of the curve to delete it.

Tap Reset to reset the curve and remove applied adjustments. 

(Optional) To adjust the color balance, choose the channel you want to adjust — Red, Green, or Blue.

(Optional) You can also select the Draw option and draw a custom curve to apply your adjustments to the composite.