Hola Rafael,

By using Custom CSS you should be able to change some colors, also for submenu items.

Here is example (for main and submenu):

.sp-megamenu-parent > li > a {color: white;}
.sp-megamenu-parent > li:hover > a {color: red;}
.sp-megamenu-parent .sp-dropdown li.sp-menu-item > a:hover {color: red;}

I hope you read Helix documenation to know where to use it.

About text color in Search field. Use that Custom CSS:

.mod-finder input[type="text"], .mod-finder input[type="search"],
.mod-finder .form-control::placeholder
{color: #eee;}

and about missing Search icon in Search button use:

.icon-search::before {content: "\f002"; 
font-family: "Font Awesome 6 Free";  font-weight: 900;}
.mod-finder .btn.btn-primary {
  padding: 7px 12px; border-radius: 0px 5px 5px 0 !important;}

later you should get

Do you mean without text "Buscar" in button ? Yes, should be possible.

Start from my CSS code, then check module settings. Probably it would be easier to language override phrase with empty space.