It's not a stupid question at all - if the pill you have received does not look like the pill that you were expecting then this should be your first warning.
You should be testing your pills with a testing kit (links in the six simple rules of MDMA in the stickies) - it would be very rare for a single pill out of a batch to look different so it is safe to assume your pills is not the same as the ones you may have seen already (some pills may suffer a bit wear, chipping etc).
You also have to take into consideration 'where' you have seen them - if you look at ecstasydata.org the pills looks anything from orange to white with few specks etc