neutral       das Fahrrad bicycle   blau blue           Ich habe mein blaues Fahrrad gewaschen. I have washed my blue bicycle.

Das Fahrrad is neutral, singular. Das Fahrrad is direct object (Accusative). If we check the table we can see that the ending is -es and the adjective is therefore blaues.

masculine       der Vater father   alt old         Er hat meinem alten Vater ein Fahrrad geschenkt. He has given a bicycle to my old father.

Der Vater is masculine, singular. Der Vater is indirect object (Dative). If we check the table we'll find that the ending is -en and the adjective therefore is alten.