[rodelrod]

Best reference I could find is here: https://www.lalanguefrancaise.com/articles/espace-insecable

Actually before the ":" specifically there should be a regular non-breaking space, not a narrow one. Except in Switzerland. Other punctuation marks take the narrow non-breaking space.

[TheRealPomax]

Love how it's "recommandé", "pour des raisons esthétiques."

Which I guess means we're completely free to ignore it. Pour mêmes raisons =P