Overlaying Free Hand Drawing Onto Single Image and Colorizing to Show Order?

It's been a few years since I've done much of anything in MATLAB or much coding in general but I am back again: I want to visualize my cell migration data in a similar way as shown in the attached image from this ACS Nano paper. I'd like to get feedback on my approach before beginning.

Here is my general plan:

1. Import time lapse images as individual tiffs
2. Register images to the first image in the stack with imregcorr
3. Read registered images sequentially into multipage tiff format
4. use imfreehand to manually trace cell perimeters in each frame**
5. Store trace of drawn perimeter**
6. sequentially save these freehand objects with the dime into array
7. Superimpose traces onto first page of the multipage tiff
8. Label sequence with rgb

" ** "= the steps I am not certain how to approach

Thanks in advance for the tips. I'm sure it willl be immediately obvious to many here