Basque gorri 'red'

According to the Vascologist Joseba Lakarra, Basque gorri 'red' derives from a lexeme *gorr- 'raw meat'. However, the isolationist paradigm of academic Vascology precludes further investigation of cognates in other language families. 

Considering the voiced initial stop in Basque was originally voiceless and also the trill rhotic isn't the product of gemination, the most likely candidates would be Altaic *kʰjú:ru ‘red, reddish; brown, dark’ (EDAL 1090) and IE *kreuH₂- ‘blood, gore’ (Greek kréas 'meat', Lithuanian kraûjas 'blood'), thus pointing to a lexeme *kʰruH-¹ ~ *kʰuHr- which would date back to the Upper Palaeolithic and underwent a semantic shift from 'raw meat; blood' to 'red' in Altaic and Basque.

One interesting derivative of gorri is gorringo², which refers either to a kind of mushroom (Amanita caesaria) or the egg's yolk.

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¹ IE *e is the ablaut vowel and doesn't play any role in the actual etymology.

² With the variants gorrinko in the Easternmost dialects (Roncalese, Zuberoan) and korrinko in the extinct Alavese.

Galician-Portuguese silva 'bramble' (updated)

Blackberries

Contrarily to what some linguists think, Galician-Portuguese silva, silveira (collective) 'bramble (Rubus)' is unrelated to the homonymous Latin silva 'forest' (which regularly gives Romance selva), but it's cognate to Leonese silba 'service berry', silbar, silbal (collective) 'service tree (Sorbus domestica)'².

Service berries

This is a substrate loanword *silba¹ with parallels (through lambdacism) in Romance serba 'service berry'³ (Catalan serva, Occitan sèrba, Spanish serba, jerba, sierba id., serbal, sierbal, Catalan servera, server (collective) 'service tree'⁴), Lithuanian serbentà 'currant (Ribes)' and dialectal Russian serbalína, serberína 'rose hip', sor(o)balína 'bramble'⁵, Latin sorbus 'service tree' (Spanish sorbo), sorbum 'service berry', from which derive Leonese (Liébana) suerba, French sorbe id., sorbier, Galician sorbeira, solveira (collective), Leonese  (Liébana) suerbal  'service tree'.

Although these forms show the typical IE ablaut e ~ o⁶, we also can find variants with /u/ vocalism: Leonese (Liébana) surba 'service berry', surbu (collective) 'service tree' and regional Spanish (Álava, Bureba, High Rioja) zurba, zurbia 'service berry', zurbal, zurbial, surbial (collective) 'service tree'. 
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¹ The shift -lb- > -lv- is regular in Portuguese.
² J. Oria de Rueda et al. (2006): Botánica forestal del género Sorbus en España, in Investigación Agraria. Sistema y recursos forestales, vol. 15, nº 1,  p. 166-186.  

³ The proposed connection (Pedersen) with Celtic *swerwo- 'bitter' (Old Irish serb, Middle Welsh chwerw) can be ruled out. 
⁴ The forms serbo, jerbo, selbo, jelbo are the product of a contamination with sorbo.
⁵ M. Vasmer (1955): Russisches Etymologisches Wörterbuch, p. 697.

⁶ In fact, some Indo-Europeanists reconstruct a protoform *serbh- ~ *sorbh-.

Paleo-European *abVl- 'apple' (updated)

Several IE languages of North Europe (Celtic, Germanic, Balto-Slavic) reflect a lexeme *abVl- 'apple' which is regarded as a Paleo-European substrate loanword by some specialists¹. In my opinion, a likely cognate would be Hittite sam(a)lu- 'apple (tree)', with denasalization of m and loss of the initial sibilant², which in this and other words such as sākuwa- 'eye' < IE *H₃ekʷ- 'to see' and sankuwāi- 'nail; a unit of linear measure' < IE *H₃n(o)gh- 'nail' would reflect a labialized voiced pharyngeal fricative *ʕʷ (IE *H₃) .

Therefore, I'd reconstruct a Nostratic³ Wanderwort *ʕu-malV also reflected in Basque udare, udari, madari 'pear'⁴ (with denasalization and further delabialization), and which I'd link to Nakh-Daghestanian *mhalV- ~ *mhanV- 'warm', with a straightforward semantic drift from 'warm (season)' to 'fruit'. This makes sense because the apple tree is originary of Kurdistan, precisely in the area where Nostratic was presumably spoken.
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¹ For example, Theo Vennemann links it to Afrasian *ʔa-bul- 'male genitals', which (in his own words) is "semantically unsatisfactory although phonetically perfect". See T. Vennemann (1998): Andromeda and the Apples of the Hesperides, in Europa Vasconica, Europa Semitica, p. 591-652.
² Explained by ortodox IE-ists such as Kloekhorst as the result of a "s-mobile".

³ My own concept of "Nostratic" isn't the one of a very large macro-family including IE, Uralic, Altaic, Kartvelian, etc. but a language spoken in the Taurus-Zagros mountains, where several species of plants and animals were domesticated in the Neolithic.
⁴ A variant *ʕu-manV would be the origin of Basque umao (B), umo 'ripe, seasoned' and Uralic *omena ~ *omVrV 'apple'.