There is such a big personality element to what you feel comfortable wearing that you need to take into consideration. Different personality styles will approach the matching or clashing element differently.
Those with a more Classic (responsible, mature, sensible, organised, ordered) personality will avoid clashing prints or colours. And it won't work on them (no matter their age) as it's not authentic or a representation of who they are. It's at odds.
Those who are more Creative (innovative, exploratory) in their personality will clash prints and colours and it will work (no matter their age) as it is a true representation of their individuality.
If you really want to delve deeply into what your personality style is and how you can express that it's the first step in my 7 Steps to Style program.
If you want to explore mixing prints (or clashing) there are rules you can follow which I have written about here and here. Some prints are easier to mix - such as stripes - they mix easily with many prints. Others such as animal prints and florals can be mixed too.
Matching shoes and handbags is of course not something that is modern (though someone who is Classic will still love to do so and it will work for them).
Your colour contrast level will also give you an indicator if mixing multiple coloured prints together will work for you (or not). Someone with high colour contrast (so more complementary or triadic colour contrast) will be able to mix multiple colour prints more easily than someone with low colour contrast (monochromatic or neutral plus one colour).
You may find if you have lower colour contrast mixing a print in a neutral with something in a monochromatic colour could be the way to try this trend.
How to Mix but Not Match Prints and Patterns
- If you want to try mixing unrelated colours the intensity must be the same. So muted with muted or bright with bright.
- The undertone of the colours should be the same - cool with cool and warm with warm
- The value of the colours should relate - so lighter with lighter or darker with darker (or medium with medium value).
- The density of the print should be different - so busy with sparse, small with large.
Even if the colours are not exactly in each print, they should relate and look harmonious. Otherwise you will look like you got dressed in the dark!
Mixing Not Matching Colours and Prints
So you've got a patterned skirt in multiple colours - how to pair a top that the colour isn't already in the print?
Think about working with the colour wheel.
You are looking for colours that relate to the colours in the print. One step away from the colours that already exist.
Using the same rules above of mixing similar values of colours (light with light, dark with dark etc) as mentioned above, then looking at the colour wheel and finding a colour that is next to the majority of the colours in the pattern.