Change the colour of the search button (e.g. darker #343a3f or whatever brand guidelines allow) so that it contrasts with the delivery message header above it which is of the same background colour.
Lighten the background colour of the delivery header (e.g. #E4E6E7|#343a3f)
'Search' may be the most effective bridge to a product page from any single other page (specially Google Shopping driven traffic landing on product pages, which are buried deep inside the website). The search box therefore needs to clearly stand out and be among the most inviting elements on the page.