CSS opacity and font-size

Hi,
Thanks for the great plugin!
I would like to change the opacity of the prev. and next. text.
As well as the font-size of the title and the size/color of the ‘1 out of 10’ text.
Can you tell me where to find the css file of SLB?
Thanks

https://ww.wp.xz.cn/plugins/simple-lightbox/