Use your LEGO for more than just building! Use it for Lego colour matching and patterning too!
This skill is called visual discrimination: where a child can identify a specific colour between other colours. A child needs this skill for reading one day: identifying and differentiating between different letters. While working on this skill, we also rehearsed the colours he knows and learned new ones too!
An older child can use this method for colour patterning with the ice cube tray and LEGO(or any other type of building blocks).
Patterning is a skill that helps children make sense of mathematical concepts as well as logical thinking: what comes next. Start with a simple 2 colour patterning, then 3 etc. You can add more ice cube trays too.
If you want to, you could use one colour and let your child sort according to properties: long blocks, round blocks, arched blocks etc.
A fun learning activity that uses the LEGO you already have in the house. Fun AND frugal!