With all black legs you either have a Ruddy Darter (Sympetrum sanguineum) or a Black Darter (Sympetrum danae).
Mature male Black Darters are glaringly obvious being almost all black, though the three spots in the central side panel usually still shows (even if a little obscured). Females are more cryptic but, with immature males, show a diagnostic black triangle on the front of the thorax.
Ruddy Darter colouration varies quite widely but they usually show a distinctive black “T” shape on the front of the thorax and a “Wellington boot” shape on the side of the thorax, the “toe” size being very variable.
Black Darter: triangle and 3 light spots.
Ruddy Darter: black “T” and boot shape.