Right thanks for reading, if i redesign a Linux distribution i.e change flash screen, colours, etc. will it become a separate distribution that i could then offer to the public?
Well this is tricky. If you use a different GUI from standard such as blackbox, fluxbox as the GUI vs gnomer or kde it doesn't change the distro. It's still the original distro running different software. Also tweaking / configuring or modding it or just changing the general appearance from default wouldn't be making your own distro. You technically could call it yours though.
If you change something like the kernel or anything standard with the distro, you technically could say it's a "new" distro or different distro, or you could simply call it that distro with a different kernel or modded.
For example you could take a shoe and color it red and call it your work (most of the work was already done for you but it's still your work) and call it "The Red Shoe" or a pair of Nikes colored red. Or you could use different shoe strings that stay tied better or that aren't as stiff. It's really up to you if you decide it's a new distro or not.
It's personally up to you to decide, but I'd just say it's a shoe, like I'd say it's linux.