I've been having some thoughts (based partially on comments on how quickly american culture diverged from British) on how cultures could develop on a colony. Feel free to chime in.
My first instinct was to turn towards the three-generation rule, then ended up adding memetics. The first generation on a planet sets up the social structure they pass on, the second maintain it, the third begins to question it and begin deviating. Obviously, each generation could span multiple genetic generations.
The dominant trends are cultural conservation (maintaining one culture as the first gen sees it), integration (leaving one culture for another), fusion (mixing cultural traditions together), and deviation (developing a new culture, usually in response to environmental differences).
Depending on the cultural mix of the colonists, fusion, deviation, or conservation could be the dominant force. Ideology also plays a part - a group focused on "keeping the old ways alive" would have very high conservative tendencies, with minimal deviation a as required. If a portion of the colony staff has a different culture, you would see either a response of conservation from them, or integration with minimal fusion ("your cooking is horrible! My restaurant, my grandmother's recipes!").
A group focused on starting fresh would have high fusion and deviation, very little conservation, and an odd sort of integration - the most dominant trends would become the basis that newcomers would adapt to.
Population and technology of the colony plays a huge part. Not just raw numbers and equipment, but the number of groups and the degree of interconnection between them. Groups could be defined by job, geography, resources, origin culture, etc. Interconnection is a function of membership overlap and personal connections between members of different groups. As population trends upwards, the more groups you have. Technology makes communication easier and increases the size of groups. Distance decreases interconnection and the cultural communication between groups.
As groups trend upwards in numbers or distance, the chances of two groups becoming isolated enough to begin cultural divergence from a mutual baseline increases. Decreases in communication ability or group size accelerate the trend.
Absolute population size does still play a part. Low population (3-) resists deviation, but accepted deviation catches on quickly ("I went out for three weeks! Why is everybody cooking Korean food?"). Such populations also have a high trend of fusion, as total groups is relatively low, with high interconnection ("portobello sushi with a side of chicharrones, behagen"). High population (5+ or 6+, depending on technology) deviates quickly, as the number of potential groups that are isolated from others allows more opportunities for experimentation.
And remember, as time goes by and conditions change, accumulated deviation becomes expected. Within 30 years, local conditions have caused relative deviations from the origin culture at time of leaving, while isolation from the origin culture has caused absolute deviation as it develops relative deviations from its historical self.
Professional colony planners would most likely aim for local manufacturing of TL5-6 equipment to allow communication, pull from 2-4 cultures to allow multiple potential solutions to local issues (usually, how to make the local plants tasty), and aim for a pop 4, which should allow a recognizable cultural base while still providing potential for local deviations.
Once a world hits pop7+, all bets are off. The potential deviations extends to even governments, and even the dominant base trends will deviate from origin.