4 Antares (Alpha (_) Scorpii)
The most challenging pair on our list to separate visually is this bright, naked-eye star in the heart of Scorpius (as described above). It appears orange to most observers, but when examined carefully in steady skies with enough aperture, you can see that the star actually comprises two components, separated by just 2.5 arcseconds.
Alpha (_) Scorpii does not give up its component pair easily, and not just because of their narrow separation. The bright orange light of the 1st magnitude primary (Antares A) can easily overwhelm the neighbouring mag. +5.4 secondary (Antares B) unless the sky is quite steady during your observation.
You’ll want to use at least 100x magnification to split the pair, and while Antares B is actually blueish-white in colour, it has a reputation for appearing green in contrast to the large red primary star.