You can simply add new strokes, each increasing in size, via the Appearance Panel.

Note, the strokes are all below the <Characters> item in the panel.
The initial white stroke is used to create the negative space around the characters themselves.
If you then want independent paths for each color, follow these steps:
choose...
Object> Expand Appearance
Object > Ungroup
Object > Expand
Object > Ungroup
Object > Expand
Pathfinder Panel > Merge
That will result in a separate shape for each color with the contour of the characters.
