Short answer — the best place to start is price-comparison + price‑alert tools (Google Flights, Skyscanner, Kayak/Momondo) and then check the airlines’ own sites (Emirates, flydubai, SriLankan, Air Arabia/FitsAir). Those give the widest view of current fares and let you set trackers so you can buy a low fare when it appears. (google.com)

Where to search (quick list)

• Google Flights — excellent for a calendar/price-graph view and for "Track prices" alerts. (google.com)
• Skyscanner — “whole month” and flexible‑date views and price alerts. (skyscanner.net)
• Kayak / Momondo / Trip.com — good secondary comparators and useful for alternate routing/mix-and-match fares. (us.trip.com)
• Airline sites: Emirates, flydubai, SriLankan, Air Arabia and FitsAir — check these after you find a fare (sometimes the cheapest fares or promos are only on the carrier’s site). (flydubai.com)

Which carriers to check

• Direct carriers on CMB↔DXB include Emirates, flydubai, SriLankan, Air Arabia and some regional operators (e.g., FitsAir). Use those sites for flash sales and baggage rules. (google.com)

How to get the best deal (practical steps)

1. Search broadly and be flexible on dates — use Google Flights’ calendar/price graph and Skyscanner’s whole‑month view to spot the cheapest days. (google.com)
2. Turn on price alerts (Google Flights, Kayak, Skyscanner) for the route and for the specific dates you’re considering so you get notified of drops. (support.google.com)
3. Compare the total price (fare + baggage + seat fees + taxes) — low-cost fares can look cheap until add‑ons are included. (See airline pages after you find a fare.) (flydubai.com)
4. Check alternate nearby airports — Dubai International (DXB) and Al Maktoum/DWC, and nearby Sharjah (SHJ) — sometimes flying into Sharjah or DWC is cheaper (but factor transfer time/cost). (google.com)
5. Consider one‑way combinations (different carriers outbound/return) — metasearch engines and Momondo make this easy. (skyscanner.net)
6. Book within a smart window — start tracking 2–6 months ahead for most international trips and be ready to buy when alerts hit; exact “sweet spot” varies by route/season. (nerdwallet.com)

Extra tips

• Midweek departures (Tue–Thu) often cost less than weekends. Use flexible-date search to confirm for your travel month. (skyscanner.com)
• Sign up for airline newsletters and follow carriers on social media for short flash sales (Emirates/flydubai sometimes run promotions). (flydubai.com)
• If you want hands-off monitoring, set alerts on two different services (Google Flights + Kayak or Skyscanner) — they sometimes catch different deals. (support.google.com)

If you want, I can look up current fares for specific travel dates (I’ll search Google Flights + the carriers and show the best options). If not, follow the steps above and you should spot the best Colombo–Dubai deals.