I claim the ornamental design for a paint tray, as shown and described.
FIG. 1 is a perspective showing the new design.
FIG. 2 is a top view showing the new design.
FIG. 3 is a bottom view showing the new design.
FIG. 4 is a rear view showing the new design with the opposite front side being a mirror image; and,
FIG. 5 is a side view showing the new design with the opposite side being a mirror image.
The shading lines shown in the drawings represent the approximate three-dimensional contour of the design, and are not intended to indicate surface decoration.