We're just getting started! Note that calling these "irregular verbs" is misleading: calling them "verbs with irregular forms" is more accurate. Some verbs have many irregular forms, some have just a few, and some have only one.
Most verbs that have irregular forms follow the green spelling pattern. Only 3 verbs that follow the blue spelling pattern have irregular forms, and only 2 of them have irregular forms in the present.
There really aren't very many verbs with irregular forms, around 20. The number approximately doubles when you add prefixes; for example, forms of the verbs "contiene", "retiene", and "abstiene" ("contain", "retain", and "abstain") follow the same pattern as forms of the verb "tiene" ("has").
The introduction covers the 18 most common verbs that have irregular forms, and they are divided into 3 groups of 6.