Can't say I've ever heard of swc_set_property.
Usually for each attribute you will have something like:
GET_PROPERTY COLOUR CHANGING CONTAINER.
data: lv_colour(6) type c.
lv_colour = 'red'.
SWC_SET_ELEMENT CONTAINER 'Colour' lv_colour.
END_PROPERTY.
(I'm just typing this in, haven't tested it)