You can easily add solid fill effects or gradient fill effects for the selected text in the message body. Please do as follows:

1. In the message body, select the text that you will add text fill effects for.

2. Go to the Font group on the Format Text tab, and click the anchor  at the bottom-right corner to open the Font dialog.
Tips: You can also open the Font dialog by pressing Ctrl + D keys together.

3. In the Font dialog, please click the Text Effects button at the bottom-left corner.

4. In the Format Text Effects dialog, please enable the Text Fill & Outline tab, and click the blank arrow  before Text Fill to expand this section.

5. Select one of text fill effects, and customize the text fill effect as you need.

No fill

If you do not want to add text fill effects or clear existing text fill effects from the selected text, please select this No fill option.

Solid fill

If you need to add a solid fill effects, please select the Solid fill option, specify a fill color from the Color drop-down list, and set the fill transparency as you need.

Gradient fill

If you need to add gradient fill effects for the selected text, please do as follows:

(1) please check the Gradient fill option;

(2) Select one of gradient fill style from the Preset gradients drop-down list.

If the specified preset gradient fill meets your needs, you can finish settings; if not, please go ahead to customize the gradient fill on the basis of the specified gradient fill.

(3) Click the Type drop-down list, and select the gradient type as you need.

(4) Click the Direction drop-down list, and select a gradient direction as you need.

(5) If necessary, change the gradient angle in the Angle box.

(6) Click the Add gradient stop or Remove gradient stop buttons to add or remove gradient stops as you need.

(7) Click to select one gradient stop in the gradient slider, and specify the fill color, stop position, and fill transparency for the stop as you need.
Then repeat this step to specify fill color, stop position, and fill transparency for other steps one by one.

6. Click the OK buttons to save the settings and close the Format Text Effects dialog and Font dialog.

So far, the specified fill effects have been added for the selected text in the message body.

You can select text in the message body and click the Clear All Formatting button   on the Format Text tab to clear all formatting from the selected text.