What causes acers to change colour?

This is a 6-7-yr-old Acer which really came into its own last year after a rather tough start. Last year the leaves were more of a red colour whereas this year they've developed into a deeper purple colour. It's fed fairly regularly with "Green Dream" (UK) top feed and kept primarily in the shade but does get the early morning sun.

I'd really like to get it back to its lighter colour (unless this dark is what it's perhaps meant to be?), but appreciate any info on its state

 

Hi Marley - no, sadly no idea of which Acer it is as I stupidly didn't keep a note at the time. Bought as a young sapling on Ebay. Here's the colour it was last year, which is what made me wonder why the change - maybe just age, if you're right and it's the particular variety of it perhaps?

 

Acers have been special to many gardeners who have become captivated by Oriental gardens. Botanically the Genus Acer is a popular and powerful one. In it's, shall we say, basic state. The genes and DNA of the species have the natural ability to change colour as the season advances.Advances in growin have also introduced many new traits.

 

Thanks Mike - yeh, sort of just curious about why they change colour early on in the season, just odd that this one is a much lighter colour early on - it just didn't hold that light colour very long this year unlike last year, but I appreciate perhaps it is all down to position and light levels etc. Just curious - fascinated by the botany

 

Hi @Delta as @Marley Farley says, last year was very hot. I just wonder if it was simply stressed last year - sometimes even 'normal green' plants get bright red or purple colours if too dry or pot too small. Yours is looking very healthy now.

 

Thanks so much for that info - all very interesting. Marley - it's in a container but I've got severe hand arthritis so fully repotting it has proven painful so I've just really removed as much older soil and top dressed etc. CarolineL - thanks so much for that encouragement on its health, as having just lost my best bonsai (a cascade 8-yo Wisteria to the first day of sun!) I'm paranoid on ensuring the rest of my prize plants doesn't suffer over the coming days of heat. This Acer may be heading towards getting downsized next year or the year after most likely as my hand issues are set to worsen and badly (plus have a major op on the right looming in the not too distant future). But in the meantime I want to try and keep it looking how it should . Thanks everyone.