Help with translation

Hello, I am translating a passage from the novel Our Homesick Songs written by Emma Hooper for my school assignment. I have come across the following paragraphs, where I find the simile 'It [rum] cut through the coffee like colour' particularly puzzling. In particular, what should 'like colour' mean; is this a common phrase to use?

... Don had coffee mixed with rum in an orange Thermos. He offered the lid-cup to Cora.

Thanks, she said, and took it. Drank. She'd never had rum before. It cut through the coffee like colour. She coughed and said, Thanks, again.

(Emma Hopper, Our Homesick Songs)

I would really appreciate the interpretation of a native speaker. Thanks in advance!