'My colooor never looooked so sheeemmmerry, eet just glowsh" purrs Penelope Cruz in the ad for L'Oreal's Casting Creme Gloss Chocolate.

Lucky Penelope, eh? Saving herself a fortune at the hairdressers and she gets to go out with Javier Bardem. Truly, some girls have all the luck.

So, if you reckon that a home dye-job is the way to go, you'd be forgiven for thinking it's a super-duper idea. Colouring is a skill, though, and that's why it can be so teeth-achingly expensive at the hairdressers. You won't get much change from €150 for a head of highlights -- cut and blowdry extra -- at many of Dublin's better salons, but if it's done well, it can really be worth the spend.

If you've found your Holy Grail hair tech, then my advice is to hang on to them.

Spread out your appointments by three to four weeks by all means, and between times, engage in a little extra upkeep with colour-protect care and styling products.

Home help

If this is the route you choose, then you're in luck: the market abounds with products to protect against colour-fade, UV damage and brassiness.

Colour care

The John Frieda range is great for blondes who can tone down brassiness with Sheer Blonde Colour Renew products, €8.49, or lighten and brighten with the new Go Blonder line, also €8.49. Bag them at supermarkets and chemists. Red-heads and brunettes could look to Wella Professionals. System Professional Color Saver Shampoo, €17.99, and Lifetex Color Protection Intensive Mask, €12.60, are both perfect for these hair types. Buy at Queen Beauty Emporium, Aungier Street.

Tress treat

Revlon Professional's Revlonissimo three-step treatment, €15.99, can help you to get an extra month out of salon colour. Suitable for all hair types and colours, it contains a creme gel to brighten colour, shampoo to prevent colour fade and a shine serum to smooth the hair cuticle, helping to lock dye inside. Call 01 886 9300 for your nearest stockist.

Root of the matter

You can buy wax sticks to colour in greys, but I'd go for Bumble & Bumble's clever coloured hair powders. While they're pricey at €18.50 for a small can from HQhair.com, these effectively mask roots and have a multi-functional appeal: use to add volume to fine hair; as a key for styling; or to get an extra day out of a wash and blow-dry.

Dye job

Rather go it alone? The good news is that home hair colourants have improved in leaps and bounds in recent years and there is absolutely loads of choice on the shelves. But the flip-side of such a huge selection is consumer confusion -- and the brand is the least of your worries. What do all those semi-demi-hint-of-a-tint terms actually mean?

Wash-in-wash-out is fairly obvious, but in the beauty biz, the word permanent is one that has a particularly elastic meaning: six-to-eight weeks is your lot with semi-permanent colours, and while they can't lighten hair, they're probably the best choice for a novice as the effect is temporary.

"The benefit is that the colour will cover up to 70pc of grey and look radiant and colourful, as well as having some translucency," explains Trevor Halls, Garnier's hair-colour expert. "That'll help it to look realistic and three dimensional, and if it's not quite what the doctor ordered, you can rest assured it'll wash out over time."

The next step up for the DIYer is permanent colour, which has the advantage of longevity and it can lighten as well as darken hair, so it's able to cover up 100pc of grey. "When choosing a shade, stay within two shades of your natural hair colour for the best results," warns Clairol's Neil Gogoi. "If you want super-shiny hair go for warmer shades, as ash shades will give a duller effect."

Ultimately, the key with home hair colourants is to have fairly low expectations and to understand what sort of product will work for you, depending on your needs. That way, you're not going to be too disappointed if your barnet bears little resemblance to the shiny mane on the box.

"Remember," warns Trevor Halls, "if your hair is dull, brittle and dry, then colour might not change the condition."

With all that in mind, what are the best ones to try?

Best new semi-permanent colour

Herbashine, €9.99, is Garnier's latest foray into hair colour, and it's a good 'un. On offer are 16 shades from blonde to black at supermarkets and pharmacies, and all contain conditioning bamboo extracts.

Best new permanent colour

Using new technology, Perfect 10, €12.99, from Clairol, comes in 15 shades and miracle of miracles, manages to work in 10 minutes. The brand has reduced the levels of ammonia in the formulation, which not only makes it smell better, but means it is kinder to hair, too.

Best natural permanent option

What if you're not keen on chemicals? Naturtint dyes, €13.45, can be found in health food shops and contains no ammonia or parabens. The 29 shades can be mixed to create unique colours, and they're permanent, so it will last.

The rules:

• Wash your hair the day before, and brush and section it into quarters before you begin.
• Draft in a friend to help -- no one can get to the back of their own head properly.
• Dark browns often come out black, so exercise caution.
• Definitely do a patch test first if you haven't used the brand or product before -- it's better to be safe than sorry.
• If your hair is past shoulder length use two packs of colour for best results.

- Kirstie McDermott