Top: Violin plots of the distribution of (NUV − r)₀ colours for galaxies in the lower mass sample (Box 1: −21 < M_W1 < −24 and z < 0.03) on the left and higher mass sample (Box 2: −24 < M_W1 < −27 and z < 0.10) on the right as a function of pair separation (on the X-axis) and velocity difference (red for < 500 km s⁻¹ and blue for 500 < ΔV < 1000 km s⁻¹). Note that we have slightly offset the two velocity samples for clarity. Galaxies below the dashed line are classified as star-forming. Bottom: Mean fraction of star-forming galaxies as a function of pair separation and velocity difference (same colour scheme as top panels) in Box 1 (left) and Box 2 (right). For the error bars see the text.