Thanks for using GWD.
You can change the font size of text as well as color in Timeline.
- Add a text on the stage
- Add a keyframe
- Select the keyframe just added
- Switch to the text tool
- From the top option bar, change the font size
- Hit Play button to see the animation preview
GWD does not allow changing the colors of rectangle, oval or line shapes in keyframes, but you can do so by using a div from Tag tool.
Hope this helps.