In order to change variables, go to the theme's CSS file. You'll see the following code at the very top of the file. Change values and click update. Now refresh and you'll see the updated changes.

/****** VARIABLES ******/
:root {
  --color-black: #13152B;
  --color-dark: #201D3B;
  --color-primary: #FAD072;
  ...
}

In case anything goes wrong, below is a list of all variables and its defaults.

Color Variables

—-color-black

—-color-dark

--color-primary

—-color-secondary

—-color-danger

—-color-success

—-color-light

#13152B

#201D3B

#FAD072

#149BFC

#DE2F28

#12CC37

#FFFFFF

Border Variables

--border-black

--border-light

--border-success

--border-danger

--border-radius

--border-width

var(--border-width) solid rgba(0, 0, 0, .25)

var(--border-width) solid rgba(255, 255, 255, .05)

var(--border-width) solid var(--color-success)

var(--border-width) solid var(--color-danger)

5px

2px

Font Variables

--font-main

--font-size

--font-auto-resize

--font-weight-text

--font-weight-title

'Montserrat', sans-serif

16px

calc(var(--font-size)*1.325 + .9vw)

500

800