This Tutorial extends on The Basics Of Refitting, it will teach you how to change the graphics used when the vehicles cargo type is changed.
You will need serial different Action2 IDs to be used.
You will only be changing the Action3 of your vehicle.
This Tutorial Assumes you have an open box wagon which has graphics for coal and iron ore cargo types.
// This would be an example of what you might have at the moment.
// This assumes that it is currently only using the coal graphics.
22 * 7 03 00 01 1C 00 00 00
Right, now we need to change the 00 after the vehicle ID, to allow different cargos to have different graphics.
In this case we change it to 02, since we have 2 different sets of graphics for 2 different cargos.
Now we need to add the different cargo types and the graphics which go with them.
You will need to refer to this document on the wiki to get the cargo ids. (Coloum 1)
In this example, Action2 ID 00 refers to Coal, an the wiki says coal is 01, therefore the part we need to add for it is "01 00 00".
The Second Action2 ID is for Iron Ore, the cargo id for Iron Ore is 08, therefore this part is "08 01 00".
And since the it is a Coal wagon if not refitted the fallback is the same as before. ("00 00")
// This would be an example of what you should have by now.
// white - Normal Action3
// Orange - Number Of Cargo IDs
// Blue - Coal Cargo ID and Graphics Code
// Purple - Iron Ore Cargo ID and Graphics Code
// Yellow - Fallback Graphics
22 * 7 03 00 01 1C 02 01 00 00 08 01 00 00 00
// Red - is for errors (commonly made btw)
// For example, there are now 13 bytes not 7
// So it should be...
// Green - Fixed bytes
22 * 13 03 00 01 1C 02 01 00 00 08 01 00 00 00
Well Done, your vehicle should now change graphics when the cargo type is changed. Only if the vehicle is refittable to the graphics cargo types though!