Hello I breed a few beetles:lol2:
I think the ones you have are
Pachnoda marginata peregrine
these are easy if you get the soil right if you just feed compost or other garden centre products then you wont get many larvae and the ones you do get may not reach adulthood or will be deformed. They will also eat each other if the soil is bad.
If you add well rotted wood/leafs this will then help produce much more larvae or you could get some Beetle soil. I will link a care sheet
Flower beetle care sheet
The purple ones are smaragdesthes africana oertzeni and there are lots of green beetles like smaragdesthes africana africana. But both these are smaller then Pachnoda. There are green Pachnoda but they would cost alot.
Other easy species:
Pachnoda sinuata
Pachnoda aemula