Colour and size of text and/or images is undone step by step

**Describe the bug**
Suppose the font size is set to 80px. When undoing this, instead of smoothly going back to 15px, it will reduce size by 1px with every press of undo. The same will happen for the colour - when setting it to #ff00, the colour will just be slightly less red with every press of undo.

Start by reproducing the issue after changing text or image size and colour, then pressing undo repeatedly. Trace the undo handling from the relevant entry point; done means one undo restores the previous value instead of changing size or colour incrementally.

Written by the indexing model from the issue text.