The female Common Kingfisher (only the 3rd photo) is almost identical in appearance to the male.
The difference between the two lies in the colour of the lower mandible. 
In the male, it is black, or in some cases, mostly black. 
In the female, it is orange-red, or in some cases, mostly orange-red.
Young Common Kingfishers have brown legs while adult Common Kingfishers have red-orange legs.

1st, 2nd & 3rd photo: Tam Coc, Ninh Binh, Vietnam, 9 January 2024
4th & 5th photo: Hoan Kiem Lake, Hanoi, Vietnam, 2 January 2024