I was playing Monopoly with my friend one day and I had an orange full set AND a red full set. I started to add houses to the sets. However, as soon as I added a second house onto Vine Street/New York (the formation of houses for the oranges and reds were 1-1-2 0-0-0), my friend suddenly told me that I wasn't following the rules of building evenly. According to him, I had to build houses on the reds, i.e. 1-1-1 1-1-1, before I could start on second houses.
The properties in a color group must be developed evenly, i.e. each house that is built must go on a property in the group with the fewest number of houses on it so far.
This is what the rulebook says about building houses evenly across a colour set, however, I couldn't find anything that says that houses had to be built evenly across colour sets.
Is what I did against the rules?