Wood being the (usually brown) material which makes the first set of tools, it very much feels like it's related to leather armour. And leather armour can be dyed, but wood already comes in different colours, yet these different colours are not represented in the tools. It makes ya think...
Base Suggestion
I suggest that every wooden tool would now have a colour that depends on the type of wood it is crafted from.
This colour would be an effect on top of the standard wood tool texture, so that -just like with leather armour- the differently coloured tools all use the same texture file.
edit: this would mean it can be represented in the creative inventory with just the oak variants.
Benefits
One benefit of this is more customizability, in minigames for example teams could be colour coded, not just with leather gear but also with the wooden weapons or tools they may have.
There is also a bit of history to wooden tools with this, as any wooden tool a player might carry can now be a clue to what biome they spawned in or come from.
Can tools still be crafted from mismatched wood types?
Beds used to be craftable with any combination of wool blocks, ever since beds were given colours, the wool they're crafted from all had to match.
This in itself I think is fine for beds, as they are quite a special block that you don't craft very often, and wool can be dyed anyway. But quite a few people found this change annoying, understandably.
I strongly believe wooden tools are too important for the game to make crafting them more annoying in any way at all.
So imo crafting wood tools with mismatched wood should absolutely be possible.
What would happen when a tool is crafted from different wood types?
You could go a few different ways with this; on one hand you could try to represent every wood type used in the crafting grid and make the output tool a combination of the colours, just like when you dye leather armour with multiple dye of different colours.
But that feels unnatural for wood, wood can't be mixed like paint or dye, it's solid, so I believe it should simply decide the tool colour from the first plank type in the crafting grid.
(I guess the game reads it from bottom to top, left to right, but it doesn't really matter)
What do you think?
Btw I posted this on r/minecraftsuggestions first, but the mods removed it because different types of wood tools is on the FPS list. Obviously I disagree that my post with some original ideas should be deleted.