Hi there! So if we're talking about what they "looked like" I'm assuming you meant in terms of their actual physical appearance. The short version is that there was an array of people and cultures in Iberia and their appearances varied accordingly. The racialist myth of "the white iberians before the moors turned up!" is just that - a myth. A very simplified one.

There aren't a LOT that talk specifically about how they looked physically. But there are some hints. For example, Abdul Rahman III, the first Caliph of Cordoba and one of the most famous Andalusi rulers of all time was born to a mother named Muzna. Maribel Fierro says that Muzna was a rumiyya which meant that she was a christian, most likely a northern Christian. His paternal grandmother was also the daughter of Fortun Garces, a 9th-10th century King of Navarre. And how was Abdul Rahman described? As having white skin and dark blue eyes. And he was ethnically an arab, but he obviously had some hispano-roman and probably Basque ancestry too, owing to his heritage from the Pamplona/Navarre royalty.

As a side note: I know you didn't ask this, but: Who were the people that invaded initially? "Moors" is a fairly non-descriptive and just generally not a useful term and who it refers to varies depending from person to person. Spanish people later used it to refer to Andalusis of all kinds (muslims, arabicised christians and jews) used it to refer to berbers, etc. Mostly the initial invaders early on were Berbers led by Arabs. They generally looked quite different in complexion from each other too. Berbers often rebelled and in the Chronicle of 754 as noted by Nicola Clarke, an Andalusi Christian source, wrote that an arab cavalry unit 'recoiled instantly due to the colour of the Moors' skin' and how dark it was comparatively, indicating a fairly light complexion on the andalusi arabs' part ( no surprise there, light complexions are common in many arab cultures).

In the century immediately before the Andalusis arrived on the scene the population were largely what are called Hispano-Romans, ruled by Visigoths. Isidore of Seville, a 6th to 7th century archbishop and famous scholar of his era did write about the local peoples as well. In his Etymologiae sive Origines (20 books long!) he describes 3 groups he refers to as Gallaeci, Asturi and Cantabri of Iberia explicitly. The Gallaeci are said to have a light complexion, moreso than all the other Hispanian people, and are described as claiming to have Greek ancestry (and he calls them cunning as a result). He somewhat outdatedly describes the Goths as wearing pigtails a lot (contemporary sources don't back up the pigtails), and also describes them of "reddish in hair" as well as "tall and strongly built" but doesn't say much of their complexion (but they were Germanic, so take from that what you will).

They were by no means a single group of people. They were a diverse set of different cultures and these peoples' heritage was influenced by celtic, roman, greek, german, carthaginian, berber, arab, phoenician, and other sources over the years. That's why in one particular book I have, Lucy A Sponsler describes women in Hispano-Roman times as looking quite different depending on what part of Iberia they came from - "women of the north were tall with fair skin and light reddish-brown hair. In the central portion of the peninsula they were shorter and wiry, while in the south they were dark with lively eyes". Sponsler notes that subsequent invasions (by Germanic people, and then by Berbers and Arabs) only heightened this difference rather than creating it. This is a difference still observable today.

tl;dr pre-Islamic Iberian people ranged from light skin to dark skin depending on both region and ethnicity.