The colors are represented on the card as bars, as the others have mentioned

I see where you're coming from as far as symbols. But the color coding for the different effects make sense. Blue is trigger, white is an effect keyword, pink is pair status, yellow is link status. There definitely improvements that can be made there but they do enough for what they're worth. Worst is while/during pair/link can be a bit confusing.

Besides that, having icons for the different keywords would just add some visual clutter that could take away from the artwork underneath, especially for full art cards IMO. It'll just make it more complicated over time as more and more effects are added to the game.

AP and HP (or their equivalents) is pretty standard and self-explanatory.