So if either one is in it needs to be mauve? lol
Nope. How did you get to that?
The rule is basically saying that if they're both in then at least one of them can't be mauve. It only applies when they're both included. And when you see that they're both included you have to make sure that they're not both mauve. So maybe the L is mauve but the U isn't, or the U is mauve but the L isn't, or neither of them are mauve. That all complies with this rule. You have a problem if you have an arrangement where both L and U are present and they're both mauve.
The contrapositive is a little counter-intuitive because it basically says that if they're both mauve then they're not both included. But how can they BOTH be mauve if one of them isn't included. That seems self-contradicting. And it is, in a way (it has to do with the modal relationship between the two conditions, don't worry there's no reason for you to know that). The point is that it gives you a rule to check your arrangement - if you see that both L and U are mauve you know that there's a mistake since you shouldn't have them both in the arrangement in that case.
TopHatToad's treatment is very good and correct. Make sure you understand how s/he worked it out.
And the logical opposite of 'some are not' is 'all'. Think of it this way, 'some are not' basically means anything less than 100% (that includes 0% btw, that's why you can have a situation where neither toy is mauve), so the logical opposite will have to be 100% since that's the only possibility left. For 'some' the logical opposite is 'none'. Some means anything above 0%, so it's opposite is 0%.
Also, contrapositives like this are the reason I tell my students that they should only make contrapositives when they're not too complicated. But my approach doesn't depend on making deductions so it may not work for everyone.