[inebriate]

change it to

var value = product_option_value("men_size");
var value2 = product_option_value("colour_001");
var val1 = value.toLowerCase().indexOf("select");
var val2 = value2.toLowerCase().indexOf("select");
if (val1 > -1 && val2 > -1){
alert ("please choose a size and colour");
return false;
}
elseif (val1 > -1){
alert ("please choose a size");
return false;
}
elseif (val2 > -1){
alert ("please choose a colour");
return false;
}
else return true;

in the next few days i will be posting up a mod to check if all the options have been selected, i posted the pseduocode to it in that other thread you mentioned