Error in plugin "sass" using the gulp command to compile the Velzon template 1.8

Hello.

I encounter problems on the configuration and customization of the web template Velzon (version 1.8).
I downloaded this last update but I’n not able to compile it according the guidance and the documentation.
e.g.
yarn install
and
gulp build
reports issues on a lib.

Error in plugin “sass”
Message:
node_modules\bootstrap\scss_functions.scss
Error: $color: var(–vz-card-bg) is not a color.

185 │ “r”: red($color),
│ ^^^^^^^^^^^

node_modules\bootstrap\scss_functions.scss 185:10 luminance()
node_modules\bootstrap\scss_functions.scss 174:8 contrast-ratio()
node_modules\bootstrap\scss_functions.scss 159:22 color-contrast()
node_modules\bootstrap\scss_accordion.scss 7:34 @import
node_modules\bootstrap\scss\bootstrap.scss 29:9 @import
src\scss\config\default\bootstrap.scss 15:9 root stylesheet

Any help will be very appreciate on the guidance or consultancy on this Template.
Thanks.
Richard