The invention relates to a color display device comprising an in-line electron gun (5) for generating three electron beams (6,7,8), and a convergence unit (14) to dynamically influence the convergence of the electron beams, preferably to decrease a distance (p) between the electron beams. The convergence unit (14) comprises a ring-shaped element (21) having four coils (22) and a longitudinal axis (24). A cross-section of the ring-shaped element (21) with a plane perpendicular to the longitudinal axis (24) is a circle with the longitudinal axis as its center and the ring-shaped element (21) forming the circumference. Each coil extends over the circumference over an angle &phgr; having a value between 50° and 75°.