If you've ever watched any other matches on say an iPad the red and orange look too similar especially when they are further away.
Matchroom know exactly how many people are watching on mobile devices and saw this was a problem and changing the the orange 5 was their solution.
I agree that the orange/red/maroon (3/5/7), and also the dark blue/purple (2/4) are easy to mix up. I also would often mix up the 1 and 9 on smaller screens or lower-resolution broadcasts. So I think changing the colors to be more distinguishable, including making the white parts black on the 9+, is a great change. Heck, I've been playing with a traditionally-colored set on my home table and I have on a few occasions recently mixed up the 2/4 and the 10/12 when in the flow, obviously with no small screen or low-def excuses.
But don't make the 5 purple. The 4 has always been purple. If you want to use pink and purple keep the 4 purple and make the 5 pink. It's ridiculous to be watching a match and have no clue what ball they're shooting at because half the time the purple ball is a 4 and the other half it's a 5.
I think I understand why it happened--Aaramith's previous TV set (with white on stripes) had the 4 pink and the 5 orange. So when they decided the 5 had to change they could either have sets with a pink 4 and other sets with a pink 5, or just change the 5 and keep the pink 4. However, now they have lower-end sets with a purple 4 and their high-end set with a purple 5. So was there no other option for the 5? It's just confusing.
I think it's telling that most matches that I've seen without Matchroom's involvement seem to have the purple 4, instead of the purple 5.
I like what another poster said: if they changed a snooker ball and made the black ball now pink (and changed pink to something else) there would absolutely be outrage. Pool is no different. Hopefully they come up with a better solution.