As a starting point, the Act doesn’t say that the EC can’t choose colours etc. Going from there you have to look at the specific scheme, how large it is and the delegations and limits you have in place. The EC stands in the shoes of the OC, other than in relation to specific decisions set out in the Act.
Therefore unless you determine at an AGM that the EC can only decide certain matters or certain things have to be determined by all the owners, the EC has the power to make the decisions. The EC can also delegate specific decisions to one or more people. For example in our block we recently had to replace a major piece of common property. Two of us made all the decisions associated with that, which included types of materials used, paint colours etc. The EC signed off on the plans, the design/scope of the project, and the general colour scheme, but from there it was up to us. We have one owner who has complained about numerous aspects of what we have done, but everybody else loves it.
Democracy is a wonderful thing but in practice if you want to consult everyone you will never make any decisions and/or the end result will be a mess – as they say a camel is a horse designed by committee. That is not to suggest that people shouldn’t have a say, but if we had gone down that route we would still be arguing about what screws to use.