Color can be used in a hundred different ways. Here we see it used to prevent new readers from being overwhelmed and confused by long words. Green identifies the first syllable, while red identifies the last syllable.
At this age, even a rule as simple as "say the green letters first," is often hard to follow due to the immaturity of the prefrontal cortex. Every correct answer brings the child closer to coping with ordinary black and white text.
A child who has seen nothing but one-syllable words naturally tries to pronounce longer words as if they had only one syllable. This is especially true when early training includes many consonant blends and digraphs. For example, splashed is an 8-letter word with only one syllable. In theory, a child who can pronounce tough words like splashed is ready to say any multisyllable word, but in practice, children need practice identifying syllable boundaries. Many children are still learning to read from left to right at this stage. Working with a first color and a last color also helps prevent them from saying the sounds out of order.
The most important factor in any exercise's difficulty is the rate at which the words change. The huge letter variety in this drill makes it much harder than earlier drills which limited letter variety, word length, and other factors. A child who can cope with an exercise like this has actually begun real reading.
Here we see color used to help a new reader identify the start of the second syllable. Almost invariably, you find one syllable for each vocalized vowel, but a syllable at the beginning of a word usually starts with a consonant or consonant blend‑and may also end with one. For example, stent has blends at both ends.
This makes identifying the start of the next syllable almost impossible for a new reader, partly because they haven't even gotten used to distinguishing vowels from consonants. I recall my early confusion surrounding vowel identification only dimly.
More tips and exercise examples are coming soon.