Akagi and Kaga deck colors

I wondered why Akagi’s flight deck looks lighter in color at the stern than in the center.
At first, I thought it was due to different types of wood being used, or an attempt to reduce topweight by using lighter timber such as pine.

But in fact, the answer lies in the diagram in the second photo.
It shows the longitudinal arresting gear system — the cables were spaced 15 cm apart and were quite thin, which made the central part of the deck appear darker.

In the third photo, the same system can be seen on the carrier Hōshō.

The first photo shows Akagi in 1930, so those are indeed the longitudinal arresting cables.
They were later replaced with transverse ones — as stated by CombinedFleet:

“1 December 1932: Refit is completed. Her arresting gear is replaced with a transverse cabled system.”

Looking at the fourth photo, Akagi in 1940, we see the same pattern: the stern is lighter, but by then the longitudinal arresting gear had already been removed.

The cables were likely treated to prevent corrosion and greased, which would have stained the deck.

During the refit, the deck was only extended at the stern, not replaced entirely, so the darkened, oil-stained area remained — it’s practically impossible to scrub wooden planks perfectly clean.

These traces are clearly visible even on the transverse system.

In the fifth photo — Kaga — the transverse black lines are marks left by the arresting cables.
So regardless of the maintenance method, the fact remains that the cables definitely stained the deck.

Therefore, one mystery seems solved: the color variation on Kaga’s deck can be explained by the very same effect, since she too was equipped with a longitudinal arresting gear system, as shown in photo 6.

The same tonal difference on Kaga’s deck can be seen in that photo — the central area is visibly dirtier than the stern.

However, the reason why the forward flight deck on Kaga and Akagi appears much lighter in the 1930s is still unclear to me.
It’s possible that this part of the deck was made of pine, since there were no landing operations there and the load was minimal, as only light fighters used it.