We've created many pink and blue reading cards for you to use. As your child progresses in reading, introduce pink reading cards first. Then add some blue cards before all the pink cards have been introduced. Otherwise some children may learn the wrong 'mental model' for spelling.
Continue in the same way as you introduce more blue cards, mixing in a few green cards incrementally.
In general, you want to add 'easy' phonetic cards with a few exceptions so that children can be exposed to the inconsistencies in spelling.
A similar approach is used when introducing writing with the movable alphabet. In Montessori writing is introduced before reading. For example, we introduce the word 'the' with the movable alphabet very early on. This helps the children write real sentences.
We follow a similar approach with the reading cards to enable the reading of simple books or stories.
Remember, you have to adapt your approach to your individual children. Some children may be very interested in advanced words early on, and it's fine to introduce those words to them when they are motivated.