When I was a child and I wanted to build something very big, I did have to settle for it being more than one colour, and having to use printed parts that might not match the theme, and using LEGO that had been manufactured in the 70s and had taken a little bit of sun damage. It didn't discourage me from building the thing and sometimes we got inventive to make the build work (say, a castle with different coloured towers etc). Truly, I only learned that is was something to be upset or ashamed over when I joined the online community (which at the time was mostly ten years or so older than me and Male, with a percentage of those my age. Who were also Male mostly building Bionicle, Halo tributes and amassing Clone/Storm Trooper minifigures). By that time, I could go to a PaB wall and get a lot of parts and I had the money to do it too, so it wasn't a big deal and I still cheerfully shared old photos of childhood builds.
I found when displaying alone at a comic con (the only LEGO presence in place) where I brought along a big bin of clone parts, the children didn't care too much about matching colours either. But that is just anecdotal.