So it's general knowledge that the energy colors of spirits and spectrals need to match, but we've gotten some subtle indication that it doesn't have to be an exact match.

The ghost train has a teal energy color. In Chapter 4 Page 147, we see consortium members discussing what to do about the ghost train's tool. Dr. Zarei, who has lime green energy, says "My energy is a close enough shade to use and heal it... slowly."

Chapter 5 Page 5 was what originally caught my eye, since it hints at this too. Grandpa Guerra says "My student's energy is a better match than yours".

So what I can assume from this is that spirits and spectrals of not-quite-matching energy colors (like, say, orange and red) can still work together, but not as well. There's likely some limit to this, but maybe an extremely powerful spectral could use a tool of a completely opposite color.

Interesting theories! When I think of spectral energy colors, my mind immediately jumps to Page 3x52, wherein:
1) Spender is incredibly afraid of yellow spectral energy??? He's downplaying the reason for Isabel, but could it be related to the shadow spirit?
2) Grandpa Guerra only wants red tools?

1) Spender says his mind is in a delicate balance. The speculation I've been seeing is that he has two spirits: Lucifer in his sunglasses that control light (Ch. 4, Pg. 62), and the mysterious shadow spirit Spender is a medium for (Ch. 4, Pg. 129). It seems that Lucifer's job is to contain the shadow spirit, and throwing another compatible spirit into the mix would most likely cause problems, hence the "mmnnyurrh".

2) Grandpa Guerra probably wants red tools because they're a better match for himself and Isabel. He doesn't like the use of tools much, so he most likely wouldn't want to arm all of his students with tools, but he said he had plans for Eightfold (Ch. 4, Pg. 150).

That does make a lot of sense, and I have to say that I agree with both of those ideas, the first one especially. I wonder what his plans were for Eightfold though... It couldn't have been something specific to Eightfold, if any red tool would do. (Which explains his gathering of red tools despite his distaste for them somewhat.) But, why would he be gathering them? Does he want an army? Backup tools in case another one becomes unusable? Mysteries abound~