I do like the third. The pale green contrasts well with both red and blue:
From a distance, the blue and green kind of blend together, because both feel like background colors. Let me see if I can tweak something. Here I've increased the red and blue components of the blue color for the black pieces. Blue is still the largest component, but it's a little more purple for a better contrast with green, though not technically purple, since the red component is still lower than the green component.
From a distance, the blue and green kind of blend together, because both feel like background colors. Let me see if I can tweak something. Here I've increased the red and blue components of the blue color for the black pieces. Blue is still the largest component, but it's a little more purple for a better contrast with green, though not technically purple, since the red component is still lower than the green component.