A card game - variation on Happy families. More than two players are needed. cards are dealt out and students take it in turns to ask "Have you got..a blue 4?" They have to collect a whole set of either one colour or a number sequence. Cards can be used to practice as many numbers as you like (1-20), for example start with numbers 1-5, with more advanced students try a whole set of 1-20.
Another variation would be just collect a set of the same number in a predetermined set of colours *- e.g. a set of number 1 in red/blue/green/yellow only.
I recommend to print out on A3 sheet of paper and laminate for durability.