I did a quick render showing how close these color codes are, at least as best I could based on the RGB values I have on hand for them.
If you look closely, you can see that the PBT blue is a little lighter than the ABS blue, and the PBT gray is a little darker than the ABS gray. Now, maybe Signature Plastics has some new PBT colors that I don't know about that are even closer, but if they don't, then you'd probably have to go with the colors shown.
Bear in mind that in order for "Space Cadet", as a colorway, to look right you need white or off-white legends, which Signature Plastics can't do (via double-shot legends) with PBT yet, at least not that I'm aware of.